Welcome! I agree that the book the previous poster recommended is the best book out there. Lots of good pet stores have it, or you can get it from Kathy Love's Cornutopia site. You can also use the search function on this site to find answers to your questions.
That said, a 20 gallon long is generally recommended as large enough for an adult corn snake. Most people keep hatchlings in a shoebox size container, or at the largest, a 10 gallon to start.
Paper towels are, I think, the best starter substrata, as it lets you monitor "bodily functions." They are rather shy, especially as hatchlings, so you want to give them lots of places to hide. They can get stressed out with a too large enclosure with not enough places to hide, and that can cause feeding problems. But in general, most of them are little pigs. For hatchlings the size of yours, a small pinkie about every 5-6 days should be enough at first.
Make sure that they have a water bowl that is big enough for the whole snake to fit into, but not huge or deep, so they can get back out.
Temperature range should be mid 80's on the warm side, and mid 70's on the cool. For just one, an under tank heater works, or a low wattage red bulb. Naturally, you want to take the temp at floor level. No special lighting is needed, as they are most active at dusk and dawn, but they :sidestep: can be out at other times.
Most people seem to just use normal house humidity, although you can lightly mist the cage when they get ready to shed, or put a moist hide in for them to regulate their own humidity.
That should at least get you started, and I'm sure that others will chime in. I've only been into corns for a few months. The biggest problem seems to be keeping from handling the cuties for the first four days or so, until they get settled in! And, of course, it's oh, so, hard not to get more! Be warned; they are addictive!
Best of luck with your new baby!
