I would probably use the universally understood "excuse me" to get their attention. Just using "waiter" or "waitress" would definitely be perceived as being impolite!

Excuse me Miss/Sir? would be polite.

Servers have tough jobs, and I try not to make their life more difficult. Personally, I ask the name of a server and inquire whether I may address him or her as such. In my opinion, calling "waiter" is brusque. Using "sir" or "miss" is also an option.

'Sir' and 'miss' would be polite, but are far too formal in my opinion. I normally do it the same way as Greg, although my dad usually does it the same way as Randy.