things you need for a corn snake
1. The cage or tank
2. That book mentioned by kdickens above, or a similar book.
3. Fresh water daily
4. a method to provide and regulate the correct temps. Ideally, 1/2 of the cage heated 82 to 88 degrees, the other half unheated 70 to 77 degrees. You should never force a pet snake to endure a cooler or warmer temp than it wants unless you have plans to force the snake into winter hibernation which some owners do. However if you don't know what you're doing, you can kill the animal. As an active pet snake, It should be the snake's choice to warm up or cool down, and we as owners provide that opportunity by providing a temperature gradient within the snake's housing.
5. Places to hide. Snakes like to stay hidden. More places are better than fewer places. There should be at least 1 opportunity to hide on the warm side of the cage and 1 as well on the cool side.
6. Corn snakes are "Rat Snakes." All Rat Snakes are good climbers, and so a taller cage with vines, and branches to climb on are often preferred.
7. A proper meal every 5 days (babies), every 7 to 10 days (adolescents) and every 14 to 21 days (adults).
8. And most important, a Willingness on your part to care for the animal, and not just a Desire to have an unusual pet, stuff it in a box and forget about it after a few weeks, which unfortunately happens too often with reptiles. Keeping a pet snake is nothing like keeping a cat or dog.