make sure you pour a good beer, they always look at this.
Never stand around doing nothing, if there is no customers, go clean ashtrays, pickup glasses, wash glasses, restock the bar, clean the bar, clean the pokies area, wipe tables, DO SOMETHING. once yoou get the job then you can slacken off and stand around when thers nothing to do. Focus on serving behind the bar because thats what they want to see. Try make jokes with customers make them laugh and be happy etc, have a chat to them w hile you pour their drinks and stuff. if they are having spirits, white spirits eg vodka gin etc ask if they want a lemon garnish in there if brown spirits scotch whiskey etc dont ask.
bar work is pretty simple, the most important thing is being able to pour a good beer with about 1.5cm head on it. if you dont know how to do something dont pretend you do just ask. the other staff will help you.
ask the othe staff if they pay on the books and how much an hour you should be getting, cos alot of bar jobs are off the books and they pay you like $11 an hour (stingy i know) so you gotta check up before you start working, and its easier to ask other staff than it is to ask your boss i think.
hope this helps, good luck you`ll do fine