The correct way to travel with your suit is to pack it in a garment bag, but with the prices airlines are charging for checked bags, it's hard to spend so much to pack one suit for a short trip.
An alternative is to use an old-school butler's trick by folding it into itself, and packing it with your carry-on. Check out this video for the technique.
By using the suit pants to fold the jacket onto, you'll create padding so the jacket and pants can't become creased.
(I've started the video 4 minutes in, so it's only about a minute.)