Tipping can sometimes be an awkward subject to talk about. If you've ever worked in the service industry then you're probably a good tipper because you know what it's like to have a good day and a bad day of tips. Below are a few tips about tipping your hairstylist <---see what I did there? ;)
1. At the moment, I don't work for a salon which means I get to keep 100% of whatever I charge my clients for their services. If your stylist works at a salon, chances are that a (sometimes large) percentage of each clients' service fee goes to their salon. If that is the case, I would recommend giving your hairstylist 15-20% on top of what you pay for your services. Also, don't ask them what percentage they pay their salon (nobody asks you what your salary is).
2. Assistants need tips just as much as stylists do. If someone besides your stylist washed or blow dried your hair then they are probably their assistant. When I was an assistant in New York, clients would tip me 5$ for a shampoo and between 10 - 15$ for a shampoo and blow out. 20$ if it was a really amazing blowout. Note, I am not recommending percentages here, be generous with assistants! They work long, hard hours and usually don't get paid much.
3. Tip for free bang trims. $5 will do. If your salon has you pay for bang trims then I wouldn't tip because I think bang trims should be free.
4. Holidays. Tip away! Your tips are your hairstylist's end-of-year bonus.
5. Gifts instead of tips. Hairstylists love gifts instead of (or along with) tips. Whether it's a Chanel bag or box of chocolates, they'll love it. ;)
*Disclosure: I worked at salons in New York City where haircut prices are much higher than most cities in the US. That being said, if you're wondering what's right in your situation then ask the receptionist at your salon. They'll know how much is normal without having an awkward conversation with your stylist.