I like to keep things simple in this regard, manners will get you a long way, if I see any shoving I will not be helpful to them, but it will always be first come first served. If there is a line across the bar, depending on which station I am at I would probably sweep left to right. Also if it is at all possible, take more then one drink order at a time. Ask if anyone is buying a single drink and if they are serve the 'singles' at the same time.