@Wisdom_HQ I always tip a minimum of 20% but for those who don't, 15% is the tax X 3 which the bare minimum. You shouldn't go out for table service if you're not willing to tip AT LEAST 15%.
@AVGirl4Life 20-25% was the norm when I was a server. $35 on an $85 food bill is a great tip but 40% is a very high expectation. Of course it happens but usually only when the service is exceptional OR with regular customers who know you & personally request you as their server.