Originally Posted by Juicy D. Links

Barbers, salons, spas
Barber - $2-3
Hair Stylist or Color Specialist - 10-20%. $3-5 extra for last-minute service.
Shampoo or other assistant - $2-5 for each person. Hand the tip directly to the person providing the service.
Manicure or Facial- 15%
Massage therapist - No tip if at doctor's office. 10-15% otherwise. If they come to your home or hotel room, find out in advance whether a tip is included in the price.
Electrologist, laser hair removal - Nothing.
Salon or spa package - Determine in advance whether a service charge is included. If none is included, then 10-20% split among the service providers. You can ask for it to be divided, pay each person at the time of service, or leave it in envelopes available at the front desk.