At high end restaurants with better trained wait staff- they are looking for visual cues on when to approach your table. Empty glasses, napkin on plate, menu down on table when you're ready to order, one customary check on the food shortly after it arrives, not so early that you haven't tried it though. But this is learned behavior on the part of the customer as well.

I hate that it's impolite to wave waiters over as well though. That would make the whole process a lot easier.