Whenever I open a tab, I usually make sure I introduce myself to the bartender and I get his name. Next I make small talk with him/her (a few seconds or minutes), so that there is somewhat of a rapport established. Lastly, I make sure to let them know that I am the only one able to place an order on this tab. (Sometimes, I give them my license and make sure they clip it to my credit card, so that there is a picture they can refer to. Although I don't do it often because of fear of identity theft.)
Not to say that by doing the above will prevent overbilling everytime, but I've found it has helped me avoid it more than a few times.
Not to say that by doing the above will prevent overbilling everytime, but I've found it has helped me avoid it more than a few times.