I think tipping is based on an understanding of the profession AND personality.
I will admit, I used to tip 15-20% before I knew what went into waiting. These days its between 20 and 35%. If you cant "afford" to tip well: skip the diet coke and put that $2 towards tips. You make a healthy choice and helped someone pay the bills.
Haircuts are EXPENSIVE. 15 bucks for a mediocre haircut (shave with a #2 + neck shave) is a lot for something that requires no skill (I do it myself these days).
Here's the best part about haircuts - they screw it up...wth! They leave fuzzies all over the place, and I have to go home and clean it up.
I ordered a shake for 2.50 at Chick fil A once and left the rest as tip - her reaction pretty much made my day
