If you've been in the city or in the US for more than a few weeks and enjoy visiting a bar, you will have probably felt pretty silly a couple of times when asked questions you just don't understand. I'm here to help and make your ordering experience at New York bars the best it can be!
The transaction at a bar is really one of the best parts about living in a big city. Depending on the venue, the bartenders may be some of the coolest and best-informed people you'll ever meet. You'll get tips and tricks about the area, you'll learn intimate histories of Greg, the guy at the other end of the bar, and you'll make some friends when you get introduced to an awesome conversation.
That being said, there are a few things that are particular to the US that will potentially not make sense to newcomers:
Table service vs. The bar
When you arrive at a place, if there's someone greeting you, you should ask “is it table service or do I go to the bar?”
The difference is important because it changes who you interact with, and it changes the tipping structure. Table service is in the busier venues with more tables that don't want everyone rushing the bar. It means a waiter will come to you and you will get your drinks brought to you.
It also means that you should only interact with that one waiter now, and everything goes through them. At the end of your night, they will bring you a check, which you should tip at 18%+ (see tipping notes below). Important note: You can't just wander up to the bar and grab a drink if you haven't got your waiter's attention in a while. You need to wait.
Sitting at the bar (or being at a venue that doesn't have table service) is slightly different and probably a little more familiar. You can pop up to the bar, you can order your drink, and you can pay cash (which ends the transaction, $1/beer/wine and more for cocktails) or you can pay card which leads to a second question:
“Keeping it open?” or “Closing out”
This threw me the first time I went to the bar, and I see it happen all the time.
They are asking whether you want to start a tab (which means they'll keep your card behind the bar) or whether you want to “close out” and pay for those drinks there and then. Sometimes there'll be a minimum order for paying with a card, so keep that in mind. There are also lots of bars which are cash only, so be aware before you order – it's not rude to ask “do you take card?”
The same bartender you started with will probably find you if you come back to the bar, but it's less important because they've already got your details.
Bar backs and Runners
At some of the really busy venues, you will notice that there are some awesome humans replenishing ice, re-filling containers, and constantly running back and forth from behind the bar.
These guys and girls are not waiters and are not bartenders, and as a general rule, they will not take your drink orders. Their job is behind the scenes support and no matter how many times you wave in their face, you won't get their attention. Be nice to them, and be friendly!
Tipping at bars
I've written enough about tipping to sink a small ship, but be sure to tip appropriately and fairly.