as a former server (turned daytrader)..
easy rule: if the restaurant has it as a price, tip on the price the restaurant gives you. I'm not too sure about 1/2 priced sushi or something like that, i just mean like specials, etc. If you bring a discount (coupon, whatever) or giftcard or get a discount from the restaurant for something unrelated to the service (bad food, not the server's fault), then tip on the original amount. Basically, what you're looking to avoid is shocking the server who thinks he's getting a certain amount only to find a discount has cut his tip dramatically. I would think the half priced sushi actually falls in the "tip the bill" since it's the given price by the restaurant at the time. That one is kinda tricky bc it's the same work by the server...On the other hand, I don't know many servers who would get pissy about someone ordering 'the special' if it's lower priced. I mean, it's better to sell the pricier stuff from a server's point of view, but still. In that case, i'd err on the overtipping side, but i'm generally a 20%+ tipper anyway, just bc i know how thankless the job is.
btw, it's really ..really annoying for people who have never served or worked in a restaurant to say something like, "why do servers put up with this, choose another line of work". servers, bartenders, porters, valet parking attendants, etc know they can make more off the system than they could working retail or any other job requiring the same skills. Most don't want to change the system bc *most* will tip reasonably well and you can have a better lifestyle than you could with any other job giving that much freedom. IE, name a job at $20/hr where you can shuffle shifts, take leaves, and work 2-7 days a week, depending on what you need.
Oh, one last thing. i can see where Percy is coming from with the discounts. I don't think i've ever had issue with a place offering menu discounts and my getting tipped less. I think, the easiest way to explain it: The price on the bill is what a server is taxed based upon. If there is a discount futher down on the bill, then servers are taxed based upon the pre-discounted cost, so tip on that. IE, if you were to go to a sushi place and get half priced sushi...say your bill was something like : Sushi: 8.5, Drink: 1.50, tax, .80, discount: $4.25=6.55...then you'd tip on the 10.80. If it said: sushi: 4.25, drink: 1.5, tax: .46=6.21, then you'd tip on the 6.21. That goes with percy's: discounts to draw in business arguments. Robot parade basically has it right. I didn't realize that
. The last thing you want to do is make the server pay for serving you, which you 'can' do by undertipping. Ie, if you go to a ruby tuesday or most chain restaurants and leave 3% or less of the stated bill, the person who just worked for you did it for free or basically lost money from a different tipping guest. Most people wouldn't do that, but if you get a bad tipper combined with a huge discount, the server can get screwed for something he/she didn't really do.
wow, this stuff is really confusing