Threads on tipping often deteriorate quickly to arguments over how waiters get paid. As much as I hate to propagate the discussion along these lines, there are just a few things I feel compelled to say.
... Being a server at Denny's is considered a "starter" position to get you through college or whatever for a reason.
~G
That is just really insensitive. There are plenty of people who have a career of serving in restaurants like Denny's, and I'm sure this is offensive to them.
If you read the whole link it states that they then apply your tipped earnings toward the balance to get you to minimum wage of $6.55/hour. It then says "In all cases, an employer may take the tip credit only to the extent that employees actually receive that much in tips. "
Therefore, you do NOT lose money or owe out anything. You get minimum wage. What you mean to say is you depend on tips for a HIGHER WAGE than minimum, which is the point I am trying to make.
Sure, if a tip is added to a credit or debit card, then an employer can see exactly what the waiter gets. But for people who pay in cash, or pay with a card and leave a tip in cash, the employer is allowed (or required, actually) to estimate the tip. IIUC, usually this is estimated at 12% of sales. So if you leave a cash tip of less than 12% of sales, you are shtupping your waiter, because you have just tipped less than the amount of tip credit that the employer can take.
OK, sorry to propagate the OT posts, but back to the OPs original question.
I tip not only based on level and quality of service, but also on my opinion of how hard a waiter is trying. For example, if our waiter is a young man or woman who is clearly inexperienced, and they appear to be working hard but make a few mistakes, and apologize sincerely, that waiter is going to get a nice tip. Conversely, if a waiter appears to be well experienced, doesn't pay a lot of attention to us, chats up the bartender instead of refilling my water, etc., even if there are fewer mistakes, and not so much as even "I'm sorry that took so long", or blames stuff on the kitchen staff, that waiter is going to get a smaller tip than the one above.
And that's another point, waiters, don't try to blame stuff on the kitchen staff or anyone else. You are my interface with the rest of the staff. In that sense you are the manager of my service. If something else is going on in the restaurant - problems with bussing, short on bartenders, manager is being a jerk, kitchen is getting orders wrong - I consider it to be your job to get that fixed, or at least recover by (at a minimum) appropriate apologies, and perhaps perq's. If your manager has a problem with that, then I feel for you, but it's not really my fault, and it might be best if you looked for a different place to work, because that's just not right.
Anyway, my message to the OP is, tip what you feel is deserved, knowing that 12% just gets the waiter to minimum wage.
I rarely tip bus drivers, unless they do something special for me. If I make a special request of Mousekeeping or make a particular mess one day, then they get a little extra. Generally I don't tip Mousekeeping routinely; they are not subject to "tip credits" taken by their employer to lower their wage, so tipping is not really required or expected, but I understand how some people feel they deserve a little something each day, and that's fine. It's becoming more customary to tip the cleaning staff in this country than it has in the past, especially at vacation resorts. I never do it on business travel unless, as I've said, they do something special. And, by the way, we
always get towel animals and other nice things (like decorating the window with our kids toys, etc.) even if we leave no tip at all.
At the bar, I know it's difficult for people from the UK because it's totally different. Generally, if I am sitting at the bar, I tip when I leave. Usually about the same as a restaurant: 12% for poor service (less if it is dismal), 18% for very good service, more for something special. If we are standing or sitting in an area where there is no table service, I tip as I order each drink (or round) from the bar. If there is table service and we are running a "tab", then I tip at the end, otherwise if we are paying for each drink (or round), I tip as I pay.
At a relaxed bar, if you are not running a tab, the custom is often to take some money out in the beginning and leave it on the bar, and the bartender will take out for drinks as you go along (and let you know if there is not enough!), and then you tip at the end. At a "higher end" bar, sometimes they do not want money all over the bar, and they ask you to run a tab, unless you are just having one. In that case, you pay when you are done.
I think that most other advice you've been given above by other posters has been pretty good. In any case have a magical trip!