Tarantula Care and Housing
Most tarantulas will thrive in the simplest enclosures. New owners sometimes make the mistake of buying tons of 'cage furniture' like fake plants, fake caves, or lots of logs. Most of these will be ignored by the spider and probably just take up space. Here is what you need to adequately house your spider.
Containers
I prefer 2.5 gallon glass tanks for my largest spiders, everything else goes in small plastic pet pals, plastic shoe boxes or various small plastic storage containers. Spiderlings are kept in plastic vials. Keep in mind the spiders preferred habitat, terrestrial spiders need more floor space than height, burrowers will need a bit of height to allow for deeper substrate and arboreals should have a container that is vertically oriented.
Substrate
This is key. So many people are given wrong information by pet store regarding substrate. You should avoid: corn cob bedding, any wood shavings, gravel and bark chips. The best substrate also happens to be the cheapest, vermiculite. Go to your local hardware store or nursery and ask for fine grade vermiculite. Mix it with peat moss or potting soil (make sure the soil has NO ADDITIVES like fertilizer). You can vary the mix depending on how humid an environment the tarantula is from. For desert species I often mix vermiculite with a fine sand like Reptisand.
Water
Tarantulas need water. How much or how often depends on where they're from. All of my spiders have a shallow water dish consisting of a bottle cap or jar lid. They are given water about once a week and the spiders from humid climes are also lightly misted with a spray mister. They will drink water from a low dish. Humidity levels in the winter are key. If you live in an area with cooler temps and use any sort of supplemental heating in the winter make sure they have plenty of water. I often mist the substrate on one side of the cage to raise the ambient humidity. Most spider deaths for us seem to happen in the winter, which we've pretty much narrowed down to humidity levels.
Burrows/Hides
Some spiders will die if not provided with a hiding place or an opportunity to burrow. King Baboons and Cameroon Baboons are two species that need burrows to thrive. This can be accomplished by providing deep substrate and keeping the humidity up or even easier by providing a curved PVC tube. The PVC acts like an artificial burrow. Most terrestrial spiders will appreciate a curved piece of cork bark to hide under but it isn't absolutely necessary. Arboreals should be provided a vertically oriented piece of cork bark to anchor their tube webs.
Feeding
Tarantulas spend most of their time waiting for food to come to them. That's another reason a large cage of one with lots of extra 'stuff' is undesirable, the crickets can just hide. I feed almost solely crickets with the occasional thawed pinky for the big guys or tiny mealworm for the spiderlings. Adults should eat 1-2 crickets once or twice a week, spiderlings should be fed more frequently. I don't power feed any of my spiders, all this does is force them to grow faster and possibly shortens their lifespan (especially if they are males).