i put "depends" so let me explain...
i normally tip - even if you don't do a stellar job i will just give you a lower tip as a cue to do better next time. (and believe me, i'll tell you what you did wrong...
) and i am a generous tipper too. especially if i think you give exceptional service. my recent trim and re-layering... that lady was not only super-friendly, but i believe she has good knowledge of actual
hair care, not just styling. i tipped her 35% because:
1) what i just mentioned (friendly, knowledgeable, and LOVED the style), and
2) i want her to remember me as the generous tipper so she will continue to give me exceptional service.
*i've been known to walk out on bad stylists though... shampoo or half a set of rollers still in my hair. so... needless to say, they didn't even get paid, let alone tipped...
(thankfully this was a rare occurance)