Bottomline: Be nice to your bartender. Here's a list of 5 things that you may be doing and it's ruining your bar experience.
If you've never waited tables or worked the bar, chances are you're not aware of the high-stress, low appreciation of the service industry. Rude customers seem to be a given but it doesn't have to be. Avoid yelling, snapping your fingers, whistling, being too touchy, and invading their personal space. While most bars are loud, bartenders are accustomed to the noise and can most likely make out what you're saying.
Tapping your foot and rolling your eyes while waiting for a drink is never a good look. What makes it worse is when it's your turn to order...you don't know what you want. When your bartender has 10, 20, 30 other people around, it's an added stress to figure out what drink you'd like. When that same person then complains about it, says it's not strong enough, or not what they're used to, it just makes you look that much more foolish.
Don't say, "I'll take care of you before I leave". Everyone says that and most never follow up with more than a couple of dollars.
Make a Mess
Tearing up your straw sleeve. Ripping the label off your beer. Doing drink coaster origami. Chewed up straws. These things belong in the trash not littered across the bar.
Close Your Tab, Start a New Tab
This ties in with being indecisive. Multiple open/close/open/close tabs might not seem like a big deal but multiple that with a full bar and you can see the disruption you're causing. Close that tab with confidence!