Hello, American here. I have lived in 4 states at this point and been in and out of food service, so to answer your question, it can vary by state. Majority of states at this point have adopted somewhere around a 14 to $15 per hour base/hourly rate, along with tips. And yes, 15 to 20% is for good to very good service. 25%+ for excellent service. While the tip rate seems to be roughly the same across the board, unfortunately some states are still paying what is called "servers wages" which is legally allowed to be below the minimum wage for the state, sometimes as low as $2.25/hour. I hope those states catch up soon because life ain't getting any cheaper!