I tip the lady who cuts my hair and my massage therapist very well. I want them to go above and beyond to take good care of me. And I see them monthly and want to have a good relationship with them.
At a restaurant it totally depends on the service. If everything is good I'll gladly give 20%+. Have no problem tipping less than 20% if I only see my waiter once or twice and don't get good service.
Hate tipping pizza delivery guys and usually only give a dollar or two because I feel bad giving them nothing even though that's what they deserve. I hate paying for the delivery and also being expected to tip. It makes no sense.