"Oh wait can you chill mine?"
Chilling a shot... a lot of people tend to order chilled shots because they can't handle a regular shot, don't like what they're drinking, etc. Fine fine fine, order your shot chilled when you're getting your own drink, but if your friend orders a round of tequila shots for everyone, are you really gonna be 'that guy' who makes everyone wait because you asked the busy bartender to chill yours? Don't be that guy!
Pro tip: breathe out; get all that air out your lungs, then as your inhale back in take the shot. Trust me. It'll go down easier, and you've saved face.
"Can I get a strong long island iced tea?"
Don't be 'that guy' and come up to the bar and order a "strong long island iced tea." First off, you've already admitted to not being able to handle your liquor by ordering a sugar-y drink that disguises the alcohol. (Also we are judging you for ordering a LIIT.) Secondly, now that you've asked for a STRONG long island, you've actually done the opposite. Ask any bartender. If some guy comes up to order a "strong _______," we are probably going to short-pour you, because either (a) you're assuming we don't know to make the drink, (b) you're too cheap to order a double, and/or (c) most people who order "strong" drinks tip like sh*t. We ain't gonna waste our bar's liquor on you.
Pro tip: Be a nice human and we'll probably make it stronger because we like you!
Other "Don't be that guy!" tips & tricks:
Don't be that guy. Don't touch our garnish trays. This is not a buffet.
Don't be that guy. Don't tap your credit card on the bar top while we are making your drink. I repeat, do NOT tap your credit card on the bar top while we are making your drink.
Don't be that guy. Don't tell us that you're a good tipper. Actually, no wait, tell us you're a good tipper, because we know it's a lie and we'll act accordingly.
Don't be that guy. Don't try to weasel a "free beer" by trying to get us to "really fill up" beer backs with your shots. (Yes. People have done this.)