If it's BYOB: 20%
"I've never worked at a restaurant that did this, but the servers there are doing the same things as they are anywhere else: They're hospitable, they bring out food, clear plates, etc. When I've visited places like that, the bill comes out to a lower amount, but I still tip 20%."
If you're eating with eight or more people: Another 10% on top of the auto-gratuity (even if it's 20%)
"A lot of times when you go out with that many people, there are people at your table you can't control. Your co-worker's husband joins you or something. If I go out with a big group and someone is being difficult, then I'll always leave extra. Definitely more than 20%."
If you get food/drink comped: 20% of the entire bill, including the free stuff
"You should tip on the full amount because you still received the full service. It doesn't matter whether you got a friend discount or if the kitchen screwed up, you should still tip on the original amount. I get screwed over when that doesn't happen. It makes me regret doing them a favor if I took stuff off the bill in the first place. Sometimes the table assumes a screw-up is my fault, so I get punished when the bartender took too long or the kitchen f**ked up. It all reflects on me."