Don’t keep the staff from their work. This happens a lot with bartenders. Bartenders are there to talk to a certain extent, but say you’re sitting at the bar waiting for your friends to show, learn to be comfortable sitting there by yourself enjoying your drink: don’t need to talk to someone and monopolize the bartender’s time.
Consider how much space you’re taking up. If you’re 2 people sitting at a table for 4 and it’s busy as hell, well, just avoid getting into that situation. Don’t pile your bags and jackets on chairs other parties could be using. Don’t pull a chair from one table to another without assessing the situation: for example would that extra chair get in the path of the staff or other people?
Know what you want before asking for the staff’s attention. Or, if you have some questions, have your potential orders in mind. Look around for a menu or a bar list before asking what’s available.
Tip well. Especially when you’re in a group and you’re splitting the bill, in fact in this case you should over tip because other people in the group will surely be under-tipping. If you don’t have the money to tip you don’t have the money to drink.
If you’re cut off, take it gracefully. So what if some bartender thinks you’re too drunk? Just leave and go to some other bar. I always think it’s ridiculous when someone throws a fit because they’re cut off: if the staff didn’t think you were too drunk before they sure as hell think so now!