If he's in a tank (with a screen lid) cover 2/3 of the lid with plastic/foil, making sure to avoid the light (if there is one). Misting the enclosure a few times a day will also help. Just make sure the substrate doesn't become soggy/wet and their is adequate ventilation.

The link below is a good place to find a herp vet in your local area. Click the state you're in and look for one that is local to you.

http://www.herpvetconnection.com/