You never say "please" or "thank you."

Whether in a restaurant or in the rest of your life, this is a sure sign of jerkdom. I'm fond of Beau Brummels definition of a gentleman: "Someone who is never rude casually or inadvertently, but only when he intends to be."

Not particularly hard. Nothing wrong with saying "please" and "thank you" especially if you're getting a good service.

It really isn't hard to say 'please' and 'thank you.' Such common courtesies go a lot further than you think.

It's an obnoxious thing to not do, but it's still not nearly the worst offense on this list.  I'd rather someone be passively rude than actively obnoxious.

this is quite rude. i am sure that waitstaff appreciate being acknowledged for their work{along with a nice tip} instead of ignored. I may not be perfect but I always say please and thank you.