Bathing on Erev Shabbos:
It is a Mitzvah [upon both men and women] to initially bathe one’s entire body in hot water on Erev Shabbos [and Erev Yom Tov] in honor of Shabbos [and Yom Tov]. If one is unable to do so then he is at the very least to wash his hands, feet and face in hot water.
When on Erev Shabbos should one bathe: It is proper for one to bathe himself as close to Shabbos as possible, and then immediately put on his Shabbos cloths. [This however only applies when bathing in one’s home. If however one is bathing in a bathhouse, as is customary when going to Mikveh on Erev Shabbos, then one should visit the Mikveh with plenty of time still left in the day. If one however plans to merely [rinse and then] immerse in the Mikveh, he is to visit the Mikveh as close to Shabbos as possible.]
Miscellaneous laws associated with bathing:
The order in bathing: When bathing one’s entire body one begins with washing his head, as the head is the king of all the other limbs. Regarding the rest of the body one first washes his right side and then his left, [thus honoring the right].
Avoiding scorching water: One who is accustomed to pour very hot water on his skin [should avoid doing so as it] can lead to leprosy.
Drying one’s face:  One should dry his face thoroughly after washing them as not drying the face properly can cause his skin to crack or break out with boils. If one did not do so then his cure is to wash his face many times in water that had beets/spinach [cooked] in it.
Drying one’s feet: One who washes his feet and places his socks or shoes on prior to drying them, can bring him to become blind r“l. [Therefore one needs to dry his feet prior to putting on his [socks or] shoes as is the law regarding all matters which endanger a person.] [Nevertheless, the populace, including Rabbis and other G-d fearing Jews, are not accustomed to dry their feet, and nevertheless G-d protects them from danger. Thus, being that this is the custom, and G-d prevents the danger from occurring, one may even do so initially.]
Does one fulfill the Mitzvah if he bathes in warm water rather than hot water?
It requires further analysis if one fulfills the Mitzvah of bathing if he bathes in warm water. Regarding the definition of hot water versus warm: The Tehila Ledavid learns that all water which is warmer than body temperate [98.6], or its heat is felt in it is considered hot water. So is implied also from other Achronim. However, there is room to learn from Admur that so long as the water is less than Yad Soledes then it is not considered hot.
What is one to do if he will not have time to bath or shower on Erev Shabbos?
In such a case then he should bathe on Thursday, or the closest day possible to Shabbos.
Not to bathe too close to Shabbos:
One is to be careful, and warn others against bathing too close to the beginning of Shabbos, as even if one will be able to finish bathing before sunset, he may come to squeeze water from his towel or hair and come to transgress.
 Admur 260:1; Michaber 260:1; Gemara Shabbos 25b
 This bathing [even of the face feet and hands] is not an actual obligation, but rather one who fulfills it is rewarded, while one who does not is not punished. [ibid]
 Mishneh Berurah 260:2 brought in Ketzos Hashulchan 73 footnote 2
 The Michaber, based on the custom of Rav Yehuda Bar Elay in the Gemara ibid, rules that the Mitzvah is to wash only one’s hands feet and face. The Rama extends this Mitzvah to one’s entire body, and so rules Admur here.
Ruling of Yaavetz-Not to enter entire body into hot water: The Yaavetz in his Siddur rules that one is to bathe his hands, feet and face in hot water. One is not however to enter into a bathhouse as doing so can cause difficulty in marital relations which is supposed to be performed on Friday night, as is written in the laws of Derech Eretz. Practically, Admur does not mention this ruling of the Yaavetz, despite him mentioning other matters [i.e. eating garlic] which are to be done to enhance Tashmish, and we thus see he does not suspect for this at all. Therefore, it remains a Mitzvah upon all to bathe their entire body in hot water on Erev Shabbos as rules Admur. Furthermore, even according to the Yaavetz if one’s wife is not pure, he too would agree that one is to bathe his entire body in hot water. Furthermore, even when she is pure it is likely that the Yaavetz was referring to the bathhouses of the past which consisted of an entire lengthy bathing ritual of sauna, steam room and hot tub. Thus, mere showering in hot water was not being referred to, and hence remains a Mitzvah upon all to perform. To note however from Kitzur SH”A 72 which states that the Yaavetz rules one is not to bathe his entire body in hot water without mentioning the idea of a bathhouse, as is the original words of the Yaavetz. However, see also the following Poskim that the issue of bathing in hot water on the day of marital relations only applies to excessive bathing: Makor Chaim of Chavos Yair 240; Aruch Hashulchan E.H. 25:3; See Upikadeta Navecha p. 51. And many Poskim also rule that the matter is not forbidden from the letter of the law, and is just a health adherence: M”A 240:29; Elya Raba 240:23; M”B 240:54
 One does not fulfill his obligation with bathing or showering in cold water. It requires further analysis if even warm water is valid. [Biur Halacha “Bechamin”]
 Admur 529:2
 The M”B 260:4 notes that washing the feet is no longer an obligation, as it was only require to be done in times that people walked barefoot as opposed to today.
 Hence in the winter when the days are short and not much time remains for the mother of the home to shower, she can simply wash her hands face and feet in hot water. [M”B 260:2]
 Biur Halacha 260 Lachof.
 So is implied from Yoreh Deah 199:2 that Chafifah means to scrub.
 Admur 262:5
 Lit. good.
 Lit. near sunset.
 This is done in order so one only begins dressing himself in Shabbos clothes in close proximity to Shabbos. The advantage of doing so is that it is now apparent that it is in honor of Shabbos that one is wearing them. [ibid]
 As we suspect he may come to take his time and come to transgress Shabbos.
 Ketzos Hashulchan 73 footnote 23
 Admur Kama 2:6, Basra 2:4
 In the Mahdurah Basra Admur writes to wash the right hand first. However, in the Mahdurah Kama it implies the entire right side of the body is to be washed first.
 The Aruch Hashulchan 260:3 writes that after the head one is to wash the heart, right hand, left hand, right leg, left leg. The same applies regarding the order of applying soap. So, rules also Kaf Hachaim 260:1 based on the teachings of the Arizal.
 Admur in Hilchos Shemiras Haguf Vehanefesh 9
 Kama 4:20-21
 Lit. “Harbeh”
 Lit. Tradin. This is also called silka as mentioned in The Laws of Rosh Hashana 583. It is defined as either spinach or beets.
 So is implied from Rashi Berachos 39a “Meiy Silka”
 To note that there are opinions which hold that there is no need to dry the feet if he is putting on socks, however this is not the ruling of Admur. [Rebbe in Shaar Halacha Uminhag Yorah Deah page 43]
 Admur Choshen Mishpat Hilchos Shmiras Haguf Vihanefesh Halacha 9
 Ketzos Hashulchan 2:10
 Machatzis Hashekel Shulchan Aruch chapter 260. Brought also in Ketzos Hashulchan 73 footnote 1.
 Based on Teshuvah of Tzemach Tzedek, elaborated on by Rebbe in Shaar Halacha Uminhag Yorah Deah page 42.
 Biur Halacha 260 “Bechamin”
 See Ketzos Hashulchan 133 footnote 1, and SSH”K chapter 14 footnote 3
 The Aruch Hashulchan [326:3] writes that although the measurement of hot water is not brought anywhere, it most likely refers to all waters that people call hot. This ruling is also found in the Chacham Tzevi 11 which forbids for women to immerse in water on Shabbos that is called hot, rather it must be cold or slightly warm.
 In Halacha 4 [brought above in Halacha 1C] regarding water heated on Shabbos Admur mentions “even if it will not be heated to Yad Soledes”, implying that before Shabbos only water that is heated to Yad Soledes is forbidden. [Ketzos Hashulchan ibid]
 Ketzos Hashulchan 73 footnote 2
 Ketzos Hashulchan 73 footnote 2