A Halocha A Day

Haircuts on Erev Shabbos:

If a person's hair is long, it is a mitzva for him to cut it before Shabbos. It is best to have the haircut on Friday to show it is in honor of Shabbos.

Cutting Nails on Erev Shabbos:

It is a Mitzva to cut nails every Erev Shabbos in onor of Shabbos. The rema rites that one should not cut their nails in order. One should start with the 4th finger of the left hand and then to the second finger, then the 5th, 3rd and 1st. On the right hand the order is: 2nd,4th,1st,3rd,5th.

Other Poskim rule that there is no problem with cutting the nails in order. The Mishna Brurah holds its best to follow the rema's ruling.

Finger nails should not be cut on Thursday as it will then appear the nails weren't cut in honor of Shabbos as they would have started to grow already.
Some opinions hold that one should not cut their finger nails and toe nails on the same day.
Rav Yehuda HaChossid brings down, one should not cut their hair and nails on Rosh Chodesh even when it falls on Erev Shabbos.

Bathing for Shabbos:

One must enter Shabbos clean and in a state of purity. One has an obligation to use hot water while bathing. Using cold water does not fulfill ones obligation.

Shabbos Clothing:

One must dress in special clothes set aside for Shabbos. This brings honor to Shabbos. It is also a custom to wear the clothes until after Havdola has been said on Motzei Shabbos.

*Note: Some have a custom to wear Shabbos clothes until 1 hour after Shabbos.