Nanci's got it - make sure he travels on an empty tummy, then he won't regurge or poop and have to sit in it for hours.
If he's adult, put him in a pillowcase and tie the top in a knot (minding his tail!), then put the pillowcase/snake into a secure travelling box like a Critter Keeper.
For smaller Corns/hatchlings, pop them in a smaller tub with airholes e.g. a cricket tub or small sandwich box. Line the floor with a couple of layers of paper towel, and put a couple of scrunched up paper towels in, so that they have something to hide in. Ensure the lid is secured, then put the smaller tub in the Critter Keeper-style travelling box. Wedge the small tub in place by jamming e.g. face towels or old T-shirts around it, so that it doesn't move about.
Make sure that you have all of his usual kit to hand and that your first job when you reach home is to set up and get him back to normal. Also, make sure that you can get a good supply of his usual food once you're at home.
