This is just a guide, not a set of hard and fast rules. Use your best judgment.
Ye Olde Sit-down Restaurants. The federal minimum wage for tipped employees is $2.13 per hour—not much. Standard tip for seated fare is 15 to 20 percent of the total bill, but you should feel free to tip more if the service is exceptional. If you have a problem with the food or the service, don't wait until your meal is over to show your dissatisfaction by stiffing the waiter. Instead, ask to speak with a manager or owner and give the restaurant the opportunity to make you happy before you leave. If you feel your server is fully responsible for your unpleasant experience and you've spoken with the management, then your tip (or lack thereof) can reflect your displeasure.
Guzzling' Gratuities. Good bartenders are there for you: they listen to your tales of woe, serve you a smart martini at the end of the workday and can give you the 411 on the cute guy at the end of the bar. So how much to pour out for your bartender? A good rule is to tip a dollar per cocktail or a doller per two beers/sodas. If you're racking up a bar tab, you can use the same method or calculate something between 10 and 20 percent.
A Tray Buffet. This is a tricky one, and can vary depending on the type of buffet. If you eat at a place like Souper Salad, where a waiter is responsible for bringing you drinks or desserts, it is appropriate to leave around 10 percent or a dollar on the table. Otherwise, if nobody waits on you there's nobody to tip.
Takeout. You might leave a dollar for the waiter if he brings you a drink while you wait; otherwise, it's not necessary.
"Did Someone Order A Pool Boy?" The delivery guy is more than a trope in porno flicks; he has to get in his car, drive all the way to your humble abode and deliver piping hot food to your door. He deserves around 15 percent or a couple bucks for the road.
Counter Service: If you are stumped by the tip jar at Starbucks, Ben and Jerry's or Flying Star, then ponder no more. Baristas, ice cream scoopers, sandwich stuffers and burger flippers are not technically "tipped employees," so they earn at least minimum wage. That doesn't mean they're making enough to move out of mom's basement, though, so go ahead and dump your change or a buck in the bucket. If your smiley neighborhood java girl is the reason behind your latte fix, or you have been dying to catch the eye of that Flying Star hunk, feel free to leave a tip (and maybe your phone number).
Cooks: Unlike waitstaff, cooks get paid at least minimum wage but often not much more. If you really want to show your appreciation to the kitchen, you can ask the manager if they're allowed to accept tips or if it's OK for you to leave the rest of your bottle of wine for them to finish after work (waiters like that gesture, too).