The Baal Korei:
Child: A child below the age of Bar Mitzvah is not a valid Baal Korei.
Baal Korei in middle of Davening: A Baal Korei who is in the middle of Davening may read the Torah for the congregation if there is no one else available. This applies even if he is in middle of Shema, or Birchas Kerias Shema, although initially he is to try to finish until the end of the paragraph.
Review and preparation: The Baal Korei must prepare and review the reading two to three times to himself prior to reading it from the Torah. One who does not know how to read may not go up to read the Torah and is to be protested.
No one knows to read: If there is no one in the Minyan who knows to read, then one person is to read the words silently from a Chumash and have another repeat after him while reading from the Torah.
Switching Baal Koreis: Initially one person is to read the entire Keria of all the Aliyos. If in middle of an Aliya, the Baal Korei becomes unable to continue the reading, another person is to take over. It is preferable for him to begin from the start of that Aliyah.
May one read from a Chumash and then from the Sefer Torah?
One should not do so as he may come to say some words Baal Peh.
May an Ashkenazi be Yotzei the reading from one who is reading with a Sefardi accent or vice versa?
Yes. However initially one is to be stringent to have a Baal Korei read from the same dialect as the congregation. For Parshas Zachor one is obligated to have a Baal Korei of the same dialect.
May one write Nekudos in a Sefer Torah?
May one place a see through plastic that has nekudos on the sefer Torah?
No because is Chatzitza
May one read with glasses?
Yes as he always wears it and is not Chatzitza.
B. May a person who was asked to be the Baal Korei refuse to do so?
One who is offered to read the Torah and refuses to read it, his days are shortened. One is thus not to refuse being the Baal Korei once he has been [publicly] called up. [If, however, he was privately asked to read the Torah he may refuse.]
Justifiable reasons for refusal: The above prohibition only applies if there is no justifiable reason for refusing the Aliyah. If, however, there is a justifiable reason for why he does not want the Aliyah then it may be refused. For example, if he did not review the Parsha two or three times beforehand, he is not to read it and may refuse. Or, he does not know how to read it properly.
C. Laws of Keria:
Reading from the Sefer: Every word and letter must be read by the Baal Korei from the Sefer Torah. It is forbidden for the Baal Korei to read even one word or even one letter by heart.
Holding onto the Torah: The Baal Korei and Olah is required to hold onto the handle of the Sefer Torah during the reading. The Baal Korei holds onto the left handle, while the Olah holds onto the right handle.
Using a silver Yad: Many communities are accustomed to use a silver Yad for the reading of the Torah. The Chabad custom, however, is not to do so.
Standing: The Baal Korei, Olah, and Gabaiy must stand during the reading. It is forbidden for them to even lean on the Bima during the reading unless one is overweight in which case one may slightly lean in a way that if the Bima were to be removed from under him he would not fall.
May one read some of the words by heart if he cannot find the place?
May one close his eyes to say some of the words with Kavana? 
Yes, so long as he does so within Toch Kdei Dibur.
 Admur 282:5
 Michaber 139:1
 Michaber 139:2
 Rama 143:1; M”B 142/8; See Michaber 139:2; 142:2; Ketzos Hashulchan 84:9
 Ketzos Hashulchan 84:9
 Michaber 140:1
 Piskeiy Teshuvos 142/8; Ashel Avraham Butshacher
 Piskeiy Teshuvos 142/7; Minchas Yitzchak 3/9; 4/47; Yabia Omer 6/11
 Piskeiy Teshuvos 142/
 Brachos 55a, brought in M”A 53:22; Elya Raba 139:2; Peri Chadash 139:1; P”M 53 A”A 22; Levushei Serud 138; Lev Chaim 3:12 [See there that one time a person was called to the Torah and he ran out and he was later burnt to death within 30 days, as the Torah is called fire]; Toras Chaim Sofer 139:1; Aruch Hashulchan 139:4; M”B 139:1; Kaf Hachaim 139:3; 428:40; Tzitz Eliezer 14:34; It is however omitted from the Rambam, Tur and Michaber:Rama [see Elya Raba and Toras Chaim Sofer ibid for explanations of this omission] See also Levush 428 and M”B 428:19 who omit this
The reason: As the Torah is called our life, and one who refuses it is refusing life. [Brachos ibid]
 See Chaim Sheol 1:13 the Sefaradim are accustomed not to call up by name, but rather privately ask the person to go up, as if one is called up publicly and refuses his life is shortened.
 Although one all the Poskim who discuss this matter refer to a case of an Aliyah [and back then the Olah would then read the Torah], nevertheless seemingly it would all the more so apply today to the Baal Korei.
 Torah Leshma 95 and 428; See Tzitz Eliezer 14:34; Piskeiy Teshuvos 139:1
 The reason: As the danger is only when the person is belittling the Torah, as it is not important in his eyes, however when he does so for a justifiable reason he does not belittle the Torah. [ibid]
 Michaber 139:1; M”B 139:1; Kaf Hachaim 139:3
 Torah Leshma 95 regarding Maftir
 Michaber 139:3; Ketzos Hashulchan 25:9
 Michaber 139:11 as explained in Taz 139:9
 M”A 139:13 in name of Kesavim
 Michaber 147:1
 Rama ibid
 Michaber and Rama 141:1; Ketzos Hashulchan 25:10
 Michaber ibid
 Piskeiy Teshuvos 142/8; Halichos Shlomo 12/5