I had an interesting conversation with the divemasters on my last trip to Roatan. There, they are only paid in tips and, essentially, the Americans paid their "wages" b/c Europeans didn't tip. (my OP: http://www.scubaboard.com/forums/3306942-post18.html) To their credit, they treated the Europeans just as well as they treated the Americans.Europeans are known for not tipping - I don't think they are necessarly "cheap" but, when you go out to eat over there, the service is almost always included - same in places like Costa Rica. No so in the USA where many seem to "have their hand out" : )
I think there was a thread sometime back about one of the liveaboards who required the gratutity "up front" with trip payment because the the crew complained that after a week, with a european (lets call it "non american") cliental, they felt stiffed. You could say to the owners, well, pay them a living wage, but again, it is what it is.
I am one of those that wish tipping was un-necessary. But since it is, I try to be as generous as I can. When I prepare for a trip, I actually pre-plan a specific wad of cash to be used for tips. As a starting point, I plan on $5/dive for the crew, $5/day for housekeeping, $3/meal for wait staff plus whatever I expect to tip for baggage transfers. That sets my base amount and then I usually add to that pot to give me pleanty of leaway to boost those amounts up. On a typical 7 day, resort-based trip I usually carry about $250 specifically for tipping, and usually end up using it all.
Here in the States, I usually tip approximately 20 percent for meals. Mostly because it's easy to double the bill and shift the decimal point. (One poster was lamenting the change from 15% to 20% for restaurants. I think this is the reason why, everyone I know uses this method to calculate the tip.)