I'm Canadian so where I come from minimum wage is the minimum amount of money a person can make working in a company, I've never really thought about the Tipping Wage culture down in the states but I will definitely have to take it into consideration next time I'm down that way(no wonder the food's so much cheaper).
Generally speaking, up here, I tip at places where I'm waited on, tip jars are a nono. My tip is between 10 and 20% depending on the quality of the service.
I also tip cab drivers 10-15% if they get me where I'm going in a decent time without giving me whiplash.
I tip delivery people, especially if I see them in a vehicle that is clearly not a company car, because gas reimbursements haven't inflated at anything approaching the speed that gas has.
Lastly I tip at Tim Hortons which is just a coffee place, but having worked there as a teenager I know what a fast paced hell it is(seriously makes Starbucks look like the DMV).
Generally I feel tipping is appropriate in situations where the person is providing a service tailored specifically to me, in a prompt, courteous and speedy manner.
Also, as a sidenote(at least in Canada), if you're going to tip using the debit or credit machine, as some are wont to do, tip extra. Waiters are technically supposed to keep track of and claim their tips in income tax, most don't claim the tips they are given in cash because it is untrackable, however they're forced to claim their debit/credit tips as there's a paper trail.