Moshe Rabbeinu was born and passed away on Zayin Adar.One is to increase in joy on this day. Some are accustomed tofast. This is not the Chabad custom. However one should increase in charity on this day in exchange for the fast. Some do not say Tachanun on this day.
A Biblical or Rabbinical obligation: There are opinionswhich say that there is a Biblical obligation to hear Parshas Zachor. Some opinions rule this Biblical obligation is only fulfilled if one hears the reading of Zachor from a Sefer Torah together with a Minyan. Others rule the Biblical obligation is fulfilled by simply mentioning the remembrance of Amalek, and hearing it from the Torah with a Minyan is only Rabbinical. According to all the Biblical obligation is fulfilled whenever one hears the reading of Amalek from the Torah, such as on Parshas Ki Seitzei and, according to some also on Parshas Bishalach. Nevertheless Rabbinically one must initially fulfill this Biblical obligation with the reading on Parshas Zachor.
Making sure to be with a Minyan for Parshas Zachor: Being that the reading of Zachor is a Biblical obligation, one is required to arrange that he be in an area that has a Minyan for that Shabbos.
Having in mind to be Yotzei: Being that the reading of Zachor is a Biblical obligation, one must have in mind to fulfill the Biblical Mitzvah upon listening to the reading. Likewise the person reading from the Torah must have in mind to fulfill the obligation of the listeners.
If no Minyan is available: Even if one does not have a Minyan on Shabbos for the reading of Parshas Zachor, it is nevertheless to be read [without a blessing] with its proper tune. [If a Sefer Torah is available then it is to be read from a Sefer Torah. If a Sefer Torah is not available, it is to be read from a Chumash.]
If one missed Parshas Zachor: Some Poskim rule if one did not hear the reading on Parshas Zachor he can still fulfill the Biblical obligation through hearing the Torah reading of Amalek that is read on Purim. Others however argue that one cannot fulfill the obligation of Zachor by hearing the Torah reading on Purim, as it is read from a different Parsha than the reading of Zachor. According to all however one fulfills his Biblical obligation with hearing the reading of Parshas Ki Seitzei. [In such a case however one must have in mind to fulfill the Mitzvah of remembering Amalek upon hearing the reading, and some Poskim write he is to tell the Baal Korei to fulfill his obligation] Despite the above, there is a Rabbinical obligation to initially hear the reading on Parshas Zachor.
When: Parshas Zachor is always read on the Shabbos prior to Purim, which is the second Shabbos of Adar. Thus when [the second day of] Rosh Chodesh Adar falls on Shabbos, Parshas Zachor is read the week after Parshas Shekalim.When Rosh Chodesh falls on a weekday no Parsha is read on the week after the reading of Shekalim which is the first Shabbos in Adar, and on the second Shabbos, Parshas Zachor is read.
The portion to be read: The portion of Zachor is read from Parshas Ki Seitzei, from the words “Zeicher Es Asher Asa Lecha Amalek” until the end of the portion. The Haftorah of Zachor is read from “Pakadety Es Asher Asa Amalek”.
How many Torah scrolls are removed and what is the order of reading: Two scrolls are removed from the ark. From the first scroll the entire weekly Torah portion is read until [and including] Shevii. The second scroll is then placed on the Bima which is followed by half Kaddish. Hagba is then done to the first scroll. The Maftir, which is the portion of Zachor, is read from the second scroll. [The Torah scroll is to be rolled to its proper section before Davening in order to prevent delay for the congregation.]
Zeicher/Zecher: There is dispute amongst Poskim as whether one is to read Zeicher Amalek or Zecher Amalek. Practically one is to read both dialects. By the reading of Parshas Zachor [and Parshas Ki Seitzei] one reads first Zeicher and then Zecher. By the reading on Parshas Beshalach and Purim one reads first Zecher and then Zeicher. The Chabad custom is to repeat only the word Zeicher and Zecher. Others have the custom to repeat the entire verse. [By Parshas Beshalach and Ki Seitze one is to repeat the words Zecher-Zeicher/Zeicher-Zecher in both Shevii and the Haftorah.]
Must one hear the blessings of the Aliyah to be Yotzei the reading of Zachor?
Are the listeners to read along with the reader or are they to keep silent?
Some Poskim rule those listeners which do not say the six remembrances daily are to read along quietly together with the reader when hearing Parshas Zachor. Others however discourage this practice and rule one is to listen to the reading without saying the words. Practically the custom is like the latter opinion.
Must one hear Parshas Zachor from a Baal Korei that reads in accordance to his accent? Can a Sefaradi hear Zachor from an Ashkenazi Baal Korei or vice versa?
Some Poskim rule that due to the difference of dialect in the pronunciation of Hashem’s name between Sefardim and Ashkenazim, each person is to hear the reading in accordance to his custom. If he is Ashkenazi he is to hear it from an Ashkenazi Baal Korei. If he is Sefaradi he is to hear it from a Sefaradi Baal Korei.
Must one hear the reading of Zachor from a Sefer Torahwritten in accordance to his custom?
It is proper to do so, although this is not an obligation.
May one make a Minyan to read only Parshas Zachor for those that did not hear it?
Some Poskim rule the extra Parshas may only be read as part of Kerias Hatorah of that week’s Parsha, and may not be read individually. However others rule that Parshas Zachor is an exception to this rule and it may be read with a Bracha if a Minyan gathers, even if they did not hear the weekly Torah reading beforehand. This may be done any time of the day, even past Mincha. Other Poskim rule that past Mincha Gedola it is to be read without a blessing.
May one make Minyanim to read Parshas Zachor for patients in hospitals without first reading to them the weekly Torah portion?
May one bring the Sefer Torah to a different area for it to be read?
If one is physically unable to come to Shul for the Torah reading, such as one who is sick or is incarcerated in a prison, then if there will be a Minyan present, it is permitted to bring him a Sefer Torah to hear Parshas Zachor or Parshas Para. If these conditions are not fulfilled then it is forbidden to bring a Sefer Torah to another area, unless the Sefer Torah is set up in an ark some time prior to the Kriah and remains there for one to two days, [and one reads from the Torah at least on three different occasions].
May one remove the Sefer Torah and read Parshas Zachor without a Bracha if there is no Minyan?
Some Poskim rule one may remove a Sefer Torah and read it without a Bracha if there is no Minyan.
Must women hear the reading of Parshas Zachor?
Some Poskim rule women are not obligated to hear Parshas Zachor. Others rule they are obligated just like men. Practically the custom amongst many women is to treat the reading as an obligation.
May one make a separate Minyan of Zachor for women?
Must children hear Parshas Zachor?
All male children which have reached the age of Chinuch are to attend the reading of Parshas Zachor. The definition of Chinuch in this regard is when the child is old enough to understand the idea of the destruction of Amalek. Girls which have reached the age of Chinuch have the same status as women in this regard.
May a child which is over Bar Mitzvah read Parshas Zachor?
If the child has not yet grown two pubic hairs he is not to read Parshas Zachor. This can be determined by whether he has begun growing facial hair.
Noise making by Zachor:
Many Gedolei Yisrael have protested against the noise making at the end of Parshas Zachor.
 Gemara Sota 12b.
Was Moshe born during a leap year? The Gemara records a dispute on this matter: Some say Moshe was born on Adar Rishon of a leap year. Others say he was born in a regular year with a single Adar. [ibid]
On which weekday, and at what time, did Moshe pass away? Moshe passed away on Shabbos afternoon, towards the time of Mincha. [Admur 292/5]
Did Moshe pass away during a leap year? The M”A 580/20 brings a dispute on this matter. The Terumos Hadeshen 294 writes Moshe passed away in a regular year that contained one Adar. However the Yalkut Yehoshua writes that there are opinions that say Mosher Rabbeinu passed away during the first Adar of a leap Year. According to the opinion in the Gemara that Moshe Rabbeinu was born on Adar Rishon one must conclude that he also passed away on Adar Rishon, as it states regarding Moshe that Hashem filled his years that he lived an exact amount of years. [Sheilas Yaavetz 1/117; Likkutei Sichos 16 p. 344 footnote 40]
Other Opinions: Some opinions say that Moshe passed away on the 7th of Shevat. [brought in M”A 580/20] The Midrash states that Moshe was born and passed away on the first of Adar. [Esther Raba 16] However the Anaf Yosef attributes this to a misprint and it should read the 7th of Adar as stated in the Talmud.
 Hisvadyos 1988 2 p. 388 [printed in Shaar Hamoadim Adar 17] The Rebbe there states as follows: It is found that Chassidim do not mark this day with any special event. This is puzzling. Hence one is to mark it with increase in joy as is befitting of the Yom Hahilula of a Tzaddik, and especially Moshe Rabbeinu. Likewise it is also his birthday, thus giving a double reason to celebrate. [ibid] On another occasion the Rebbe stated that it should have been proper to establish the joy of this day similar to the celebration that is accustomed on Lag Baomer. [Sichas listed in Otzer Minhagei Chabad 28]
 Michaber 580/2
 As Chassidim are accustomed to not increase in fast days. [Rebbe in Shaar Hamoadim ibid; Sichas listed in Otzer Minhagei Chabad 28]
 Rebbe ibid
 The Chabad Rabbeim did not say Tachanun on Zayin Adar starting from the Mincha of Vav Adar. Nevertheless this custom only began once they took leadership of the movement and not beforehand. [Sefer Haminhagim [English] p. 168]
The reason: As the soul of Moshe shines within the leader of each generation, and hence they feel the value of the birth of Moshe on this day. [Likkutei Sichos 16 p. 350-351]
 Michaber 146/2; 685/7; Admur 282/16
 Tosafus; Rashba; Rosh [Brachos 13a]; Hagahos Ashriy Chapter 6 Brachos; Tosafus Shantz brought in Terumas Hadeshen 8; Smak; based on Megillah 18a. [See M”A 685/1; Shaareiy Halacha Uminhag 2/287]
 This is learned from the verse “Zachor Es Asher Asa Lecha Amaleik” which implies one must verbalize the remembrance of Amaleik and it does not suffice to remember it in one’s mind. [Kaf Hachaim 685/33]
 Mahram Shick Mitzvah 605
 Nevertheless, even according to this opinion, whenever one remembers Amaleik during the year, such as by the six remembrances said daily after prayer, he also fulfills a Biblical obligation. It is just that the remembering Amaleik through the reading from a Sefer Torah with a Minyan is only fulfilled once a year. [Shaar Hamoadim Adar p. 235]
 Chinuch 603; Ramban Ki Seitzei
 M”A 685/1
 Some Poskim rule the obligation to remember Amaleik applies only once a year. Meaning one is only obligated one time a year to remember Amaleik. Nevertheless, even according to this opinion, one fulfills the Biblical command every time he remembers Amaleik that year. This is similar to the Mitzvah of Tefillin of which a Biblical Mitzvah is fulfilled every moment that one is wearing them, even though he has already fulfilled his obligation after the initial wearing. Other Poskim rule the Mitzvah to remember Amaleik is constant. [Hisvadyos 1989 2 p. 442-446 printed in Shaar Hamoadim Adar 46-47]
 Aruch Hashulchan ibid
 Michaber 685/7; Terumas Hadeshen 108; Beis Yosef; Levush, brought in Kaf Hachaim 690/125
 Kaf Hachaim 685/33
 Rama 685/7
 Kaf Hachaim 685/35
 M”A 685/1 and so rules Beir Heiytiv 685/2; P”M 685 M”Z 12; Shaareiy Efraim 8/85; Minchas Elazar 2/1; Kaf Hachaim 685/28
 The reason: As it does not state anywhere in the Torah that one must specifically read Zachor from a Sefer Torah the Shabbos before Purim. It is rather an institution of the Sages that Zachor is to be read before Purim. This institution was made because on the Shabbos before Purim many people are found in Shul. Alternatively it was done in order to proximate the destruction of Amaleik to the story of Haman. However from the Biblical perspective, any time one hears the Torah reading of Amaleik he fulfills his obligation. [ibid]
 Aruch Hashulchan 685/5; Hisorerus Teshuvah 1/5; M”B 685/8; Mahril Diskin 2 Kuntrus Acharon 5/111
 The reason: They rule that the Mitzvah of remembering Amaleik is only fulfilled when one reads of the Mitzvah to destroy Amaleik, and this command is only written in Parshas Ki Seitzei which is read on Parshas Zachor, and not in Parshas Beshalach which is read on Purim. [Aruch Hashulchan ibid]
 Aruch Hashulchan ibid; Hisvadyos 1989 2 p. 442-446 printed in Shaar Hamoadim Adar 46-47
 Har Tzevi 1/58
 Aruch Hashulchan ibid
 685/2 and 5
 The reason: In order to proximities the remembrance of Amaleik in Parshas Zachor to the obliteration of Amaleik which is commemorated on Purim. [Taz 685/1]
 Levush brought in Kaf Hachaim 685/26
 The Haftorah is found in Shmuel 1 chapter 15
 Mishneh Berurah 685/9 and 12
 Pashut as this is the entire reason for why we are to take out two Sifrei Torahs.
 Shaareiy Halacha Uminhag 2/288; Ketzos Hashulchan 84 footnote 22 and glosses to volume 3 (p.74b)
 This dispute is recorded in M”B 685/18; The Rebbe in Shaareiy Halacha Uminhag ibid writes his source is from the Mesorah; Some Poskim rule the main Nussach is with a Tzeirei. [Bitzel Hachachma 6/50; Piskeiy Teshuvos 685/9] Others rule the main Nussach is with a Segal. [Maaseh Rav 134 that so was the custom of the Gra; Ketzos Hashulchan 84 footnote 22; In the glosses to volume 3 (p.74b) he proves that this was also the opinion of the Tzemach Tzedek] In conclusion the Rebbe and Ketzos Hashulchan ibid rule that by Beshalach the main Nusach is with a Tzeirei while by Ki Seitzei the main Nussach is with a Segal. Nevertheless we still read both Nuschaos as will be explained.
The saying of the Toras Chesed: The Ketzos Hashulchan ibid quotes that the Toras Chesed stated regarding this dispute “Zecher, Zeicher, the main thing is to blot them out properly”.
 M”B ibid; Ketzos Hashulchan ibid in name of Toras Chesed; Rebbe ibid
The Ketzos Hashulchan ibid writes that those which are meticulous would read it one time with a Tzeirei and one time with a Segal. By the reading of Beshalach and Ki Seitzei [when the Parsha is read twice, once for Shevii and a second time for Maftir] they would read it one way by Shevii and the second way by Maftir. By Purim and Parshas Zachor [in which the portion is only read once] they would repeat the verse twice. In the glosses to volume 3 (p.74b) he concludes that this is the custom, to read both Zeicher and Zecher, and so was the directive of Rav Shneur Zalman of Lublin, the author of Toras Chesed. To note however that there he mentions that the Baal Korei in Lubavitch stated they by Beshalach they would read only with a Tzeirei, and by Ki Seitzei only with a Segal.
 So concludes the Rebbe ibid and Ketzos Hashulchan ibid
The reason behind this order of Zeicher/Zecher: This ruling is based on the Sefer Boneh Yerushalayim which is Meyuchas to the Alter Rebbe. There it states that by Beshalach the main Nussach is with a Tzeirei while by Ki Seitzei the main Nussach is with a Segal. [Nevertheless we still read both Nuschaos as ruled the Toras Chesed.] Thus by Beshalach we first read it with a Segal [Zecher] and then with a Tzeirei [Zeicher], as the second word read is viewed as a correction and is the main Nussach. By Ki Seitzei we follow the opposite order as the word Zecher is the main Nussach.
 See Piskeiy Teshuvos 685/9
 Otzer Minhagei Chabad p. 18 unlike the custom recorded in Ketzos Hashulchan 85 footnote 22, and the supplements in the back of the Sefer, that one is to read Zeicher by Shevii and Zecher by Maftir.
 Taz 685/2; Chasam Sofer Glosses on 685
 53/13 implies there is no need to fulfill the Brachos of the Aliyah. Furthermore it is also implied from 282/16 from the fact a Katan may not read Zachor but may recite the Brachos, even though others do not fulfill their obligation with his Bracha as is proven from 53/13. See above in previous footnotes for a lengthy discussion on this ruling.
 Minchas Elazar 2/1 based on Mahram Alshiker that one only fulfills the Mitzvos of remembrance [Zachor; Shabbos] if he verbalizes the words. So rules also Shaagas Aryeh 13 brought in Ketzos Hashulchan 19 footnote 28
 Yechaveh Daas 3/53; Meishiv Davar 47; See also Ketzos Hashulchan 19 footnote 28 which negates the ruling of the Mahram Alshiker.
 Piskeiy Teshuvos 685/7
 Yabia Omer 6/11
 Sefaradim say Hashem’s name with a Patach while Ashkenazim say it with a Kamatz. [See Piskeiy Teshuvos 685 footnote 41]
 Piskeiy Teshuvos 685/10
 Birkeiy Yosef 685/3
 The reason: As we do not find anywhere that we read the Torah with only one Aliyah. [ibid]
 Tzitz Eliezer 16/21
 Sheivet Halevy 4/71; See however there that if the people who came to this Minyan are not G-d fearing, then past Mincha one should not read for them Zachor, even without a blessing, and rather they are to come for the reading of Purim to be Yotzei.
 M”A 135/23 based on Oar Zarua [regarding Zachor]; M”B 135/46 [adds even Parah]; See Piskeiy Teshuvos 135/26
 See Rama 135/14; Aruch Hashulchan 135/32; Piskeiy Teshuvos 135/25
 Kaf Hachaim 685/35 based on Rama 685/7; Kinyan Torah 7/55; See Shraga Hameir 6/116; Binyan Shlomo 54
 Chinuch 603; Avnei Nezer 509; Marcheshes 1/22; Aruch Hashulchan 685/2; Arugas Habosem 205; Tzitz Hakodesh 1/51; Hisorerus Teshuvah 1/5; Divreiy Chaim 2/14; Kaf Hachaim 685/30; Toras Chesed [Lublin] 37: “We have never heard of women going to Shul for Parshas Zachor”
 Minchas Chinuch Mitzvah 603, Binyan Tziyon 2/8; Minchas Elazar 2/1-5; Darkei Chaim Veshalom 835; and other Poskim mentioned in Sdei Chemed Klalim Mareches Zayin Klal 13
 Minchas Yitzchak 9/68
 Minchas Yitzchak 9/68
 Kinyan Torah 7/53; Shraga Hameir 6/16; Poskim brought in Minchas Yitzchak ibid
 The reason: As one should not remove a Torah from the ark for a reading which is not obligatory. [ibid]
 See 343/3
 Piskeiy Teshuvos 685/11
 Hiskashrus 109 and 1025; Yalkut Yosef 5/259
 The reason: Seemingly the reason for this is due to a Hefsek, interval, in the reading or between the reading and the blessing.