I tip 20% baseline, but then again I'm a waiter and I empathize with my kind. Never tip less for lunch. Understand that the server might get only a fraction of your tips, and that some might go to the people who sat you/cooked your food/made your drinks/cleared your mess.
Also I remember frequent low tippers and meticulously plan revenge
I really like the idea of SPope in full Damir talking about the wine list.
But seriously, we can't accept tips at my place- the people who nevertheless leave money on the counter make us happy, and even without tips the cheapskates are obvious (and kinda pathetic).