How to Pack a Suit
You have two options: Put your suit in a garment bag, which will keep it mostly crisp, or fold it in your suitcase—very, very carefully. Lifehacker has a useful instructional video on folding a suit in a suitcase, using a method created by a professional dry cleaner.
Travelers have endlessly debated the geometry of the perfectly folded suit. Some say to roll it, since folds cause wrinkles; others argue it's best to fold strategically, being careful with collars and creasing. (USA Today, for example, recommends that travelers "fold dress shirts so that the horizontal fold sits closer to the bottom of shirt; doing so will place the crease below the waistband of your pants, where it won't be seen when you're dressed.") But overall, many experts agree that it's important to sandwich the suit with a plastic dry-cleaner bag or tissue paper. Accessories like the Eagle Creek Pack-It Specter Folder or packing cubes will work too.