Restaurants or bars
If you get awful service, talk to the manager. The manager cannot correct the situation if he doesn't know about it. Skipping the tip will not accomplish anything, and the next poor customer who gets that server will get the same service you did.
If you are buying the meal and someone offers to get the tip, tell them they can buy next time, and you pay the whole thing. This prevents any uneasiness about them seeing the amount of the bill or worrying that they will be stingy on the tip.
Restaurants report a percentage (around 12%) of the gross sales for food and beverage to the IRS for their staff. This means that if you have a $200 food bill and $200 wine bill, the restaurant will report 12% of $400 or $48 as income to the server. In other words, the server has to pay tax on it whether you tip it or not. If the restaurants do not report it accurately, the restaurant and the wait staff get audited by the IRS.
Please don't get hung up on the 12%. It is just a reasonable example. I recommend tipping 10-15% on the alcohol and 15-20% on the food. 10% on the wine is perfectly acceptable. Whether to tip 10 or 15 percent would depend in large part on how helpful the server was in choosing the wine and serving it.
Food server - 15-20%.
Self-service restaurant or buffet - Nothing unless there is some service. Tip 10% if the server delivers all or part of your meal or keeps your drinks refilled.
Takeout - If you get good service, in other words, the waiter gets and packages the food, then at your choice you can tip $1-2 or up to 10%. Nothing is really necessary.
Drive through - Nothing.
When breakfast is included in the price of the hotel room - Estimate the value of the meal by looking at a menu. If there is no breakfast menu, consider the quality of the hotel and the price of an evening meal, then make your best estimate. Your tip is 15-20% of your estimate.
Teppanyaki chef - 15-20% of the total bill. The gratuity will be split among the wait staff and the chef.
Counter service - 15-20%.
Cocktail server - 15-20%. For free drinks in Vegas, tip $1-2 per round.
Bartender - 15-20% or $1 per drink. If at the bar before a meal, settle up with the bartender before you go to your table.
Wine steward or sommelier - 15% of wine bill.
If a bar has a cover charge, you do not tip on it.
Busboys - Nothing, unless he did something extra special like cleaning up a huge mess. Then give him $1-2.
Maitre d' - Nothing, unless he gets you a special table or the restaurant is full and you had no reservation. Then give $5-10 or more.
Coat check - $1
Restroom attendant - $1
Separate checks - If you want separate checks, ask the server to go ahead and add 18% gratuity to each check.
Musician that visits table - $2-3 if you make a special request. Optional if he just stops by and plays.
Musician in lounge - $1-5