The Mezzanine

As for details - your server will bring your check to your table when they think you are done eating. (If you need it faster you can always ask for it.) If you pay by credit card, then the receipt you have to sign will have a line on it that says tip: and you write in the amount you want to add to the total as tip. If you pay with cash, you can leave the full cost of the bill plus the tip and say 'keep the change' or just walk out, or, if you don't have exact change for the tip, you can ask for change and then leave what you like. The servers keep track of all their tips and then split them up at the end of the night with the various busboys, dishwashers, cooks, hosts, etc who may have also been working at the restaurant.

In coffee shops and the like, there will be fairly obvious tip jar near the register.