Besides clothes, Red Dead Redemption 2 also allows you to take care of your character's hair and beard. On this page you can learn where you can shave off your beard and how to cut your hair or change your hairstyle.
Shaving your beard is easier - the gang hideout has a special "booth" for this. You can find it near Arthur's bed. Shaving in the camp is free.
The game allows you to change the style of your beard and to adjust its length (the slide at the bottom of the screen).
You can't cut your hair in the camp - this can be done only at a barber. Barber saloons can be found in the towns. One of them is in Valentine - you reach this town at the beginning of the second chapter. The barber can be found at the back of the saloon.
Barbers offer much more options. Besides cutting hair, you can also change your hairstyle and shave your beard. All services require payment - they can cost from a few to more than $10. Depending on your preferences you can decide to, i.e. only cut the ends a little bit or shave your entire head.
Additional note - Cutting your hair or beard too much blocks you from certain hairstyles or beards. Wait for your hair to grow back and then visit a barber.
Drink Hair Tonic if you want Arthur to grow his hair back faster - this item can be bought at a general store (for about $4) or found in the game's world (i.e. in a drawer or on a corpse).
Hair Pomade is another hair product available in the game. This one makes your hair shinier - the pomade can be bought or found in the world. The first pomade lies on the chest next to your bed.