Foil on top. I lined it with plastic wrap up to the lamp and covered the rest in foil. I used the plastic wrap/foil combo and it worked well for me.
Sphagnum moss added to bump humidity over one of his hides.
Thermostat for cheap
http://www.reptilesupply.com/product.php?products_id=75
What you'll be looking for at Walmart
http://willowtreehome.com/Merchant2/...01/00891A1.jpg
Keep in mind that the whole set up was before I moved on to tub and racks. Ever since, I havent had an issue with humidity and have no reason for my big bag of moss. But some people prefer tanks, so Im not going to tell you that you need to switch or else! But there are definite ways to improve the performance of a tank.
You might want to insulate it as well, covering 3 sides with styrofoam or corkboard to maintain temps better. It'l make life easier for you, I promise.