What do you do at the end of a meal?

If you're at home, you should always at least clear your own plate.

If you're at someone elses home, you should wait until the host rises and begins to clear, and then ask if you can offer any help.

Never walk away from the table, though, just because you finish eating first. That would be ignorant.

And never - I've seen this before and it's so embarassing for the person who doesn't know any better - never scrape the food off of one plate onto another. Always do the ugly scrape work away from the guests - at the kitchen sink. Keep the table a pleasant place.