I always tip a dollar, you tip a dollar every beer, it adds up pretty quick. If it's mixed drinks, a little more may be used, but it's not hard to take a beer out of the cooler and take the cap off. In Boston bars, I don't think tipping big will help you get a free drink or anything with the bar tender. There are so many people, I really just don't see it happening. Also, half the time, the bartenders in Boston don't even see who tips them. You pay, get your drink and before you drop the tip hes on to the next person.