Moderate lighting is essential during daylight hours, and can be provided by either incandescent or fluorescent lighting, which should be off at night to provide day/night cycles.
A bowl of clean drinking water will provide sufficient humidity for most snakes.
For example, garter snakes eat nightcrawlers, fish, or frogs; water snakes eat fish; milk snakes, kingsnakes, at rat snakes eat mice and other appropriately-sized rodents (milk and kingsnakes are also known to eat other snakes and lizards); hognose snakes eat toads almost exclusively; and green snakes eat insect larva and crickets.
Snakes normally do not eat right before shedding, during mating, and when gravid (pregnant).
Providing your snake with a clean, warm, stress-free environment, and providing proper food will keep your snake healthy in most cases.