I always tip Waiter/waitress based on their performance. If they never check up on me/who I am with their tip will be less. This is if there is a valid reason for them being busy, like 2 hour waiting period to be sat. Even then, a really good waiter will do fine. (Generally 15% tip, more for that extra step they take)
Food Delivery usually always gets a tip, assuming they do things timely.
Hair stylist, I tip 30% because they do a great job where I go. For $10 I get my hair cut, shoulders massaged, hair washed and conditioned while getting a head massage (I know you're thinking something dirty...STOP IT!
) so I give them a $3 tip. Its a barbershop for men, no nothing dirty happens there, it's a legitimate buisness.
Bartenders I don't tip all that much. It's not hard to stand there and charge a shit load of money for a drink that takes you a few seconds to pour.
I rarely take a Taxi, but I guess I tip them 15%.