Personally, when I go out to drink, I leave a dollar a drink, especially
because most of my drinks are LI Iced Tea or other mixed drinks which take
longer than filling up a beer mug.
In my short-time as a bartender, I'd say that the average tip (for me) is 30%.
I only say this because some don't tip very well AT ALL (i.e. will have 4
mixed drinks and leave a dollar). But there are tippers who tip 50 to 75% in
my experience... for example, there is a regular who comes in and leaves $5,
even if he only had 2 or 3 pints of beer. Then, there are people who leave a
dollar a drink, which also makes me very happy. On the days that I work, I
usually check the total amount after zero-ing out the register... it has
averaged between 25 and 35% of the total. So even if someone leaves a bad tip,
I feel that somehow, it will manage to even out.