Because bugs aren't just for breakfast anymore...

Care

How do I care for my tarantula?

In order to answer that, I'd say that rather than run out to a pet store and speak to a clerk who knows little about tarantulas, you should simply think like a tarantula. 

What type of tarantula should I think like?

Essentially, there are two main types, arboreal, and terrestrial. Arboreals live in trees. They make good use of slightly larger, more vertically oriented enclosures, perhaps in part because of the greater air space from which many arboreal species appear to benefit. Terrestrial tarantulas live in holes in the ground. Having excavated a large number of terrestrial burrows, I can tell you that a main chamber twice the size of the tarantula is quite generous indeed. Many a smaller than that. So, a Brachypelma smithi of any size in a 29 gallon tank is simply overkill. Such a thing may in fact be harmful. A six inch B. smithi for example, can be quite successfully kept in an 8 x 8 x 12 enclosure. Rather than being cruel, this is quite ideal. Many tarantulas actually appear to feel more comfortable in smaller enclosures, perhaps coming to regard the entire enclosure as a giant burrow. A good rule of thumb for terrestrials is that a container 1 1/2 leg spans deep, 2 leg spans wide, and 2 leg spans (at most) from top to bottom is sufficient. More height introduces significant danger of falling deaths, especially for adults, and more space in the width or length department makes finding food and keeping moisture levels correct difficult in the case of spiderlings. Many spiders do best in vials, and will not thrive if immediately placed in a big enclosure. For arboreals, turn those dimensions on their side, and perhaps make them 50% bigger but remember that arboreals too can suffer from falls.  Petpals, Kritter Keepers, and New World Habitats are all successfully used by tarantula keepers, as are deli cups and vials with appropriate holes for air circulation. Avoid aquariums with dividers and screen tops, both things that lead to trapped feet and other types of problems.

What type of substrate should I use? 

Peat moss (not sphagnum), potting soil, vermiculite, and mixes of the three have all met with success. Be careful when selecting potting soil to try to get a soil low in pine family products. If it smells like an evergreen when you open the bag, allow the soil to age sufficiently for the smell to subside prior to use. The reason for this is that the scent is produced by an essential oil which happens to be a potent natural insecticide to many insects and other invertebrates that are not adapted to it. 

How about water?

Don't forget to use a water dish with all species. Under conditions such as forced air central heating, a tarantula, especially a spiderling, can dry out extremely fast. Water dishes not only provide a source of drinking water, but also a source of evaporating water which can increase ambient humidity. Increasing the size of the water dish and the surface area of the water is a great way to increase humidity, as is minimizing the amount of openings in the enclosure. Misting tarantulas is mostly a myth. For one, misting any tarantula directly will seriously piss it off! Imagine if you got your morning drink each day by being sprayed with a water hose. Please, never mist your tarantula directly. Some tarantulas will drink mist from the side of the container, but one can just as easily pour water in a stream directly on the side or simply glue a water dish such as an empty deli cup at the top of the enclosure, then set another deli cup inside of it as a water dish for arboreals. 

What about temperatures?

Contrary to popular belief, most tarantulas will do quite well in the typical household environment without additional heat. Pet stores love to sell you heaters and lamps designed for reptiles (and to increase profits) but ignore them. In a home that falls between 65 and 80 degrees, most species of tarantula will do fairly well. If you use a heater, avoid placing it on the bottom of the enclosure as most invertebrates burrow down to cool off, and placing one on the bottom will only make it hotter. Place it on the side instead. Lamps? Avoid incandescent. They dry out the ambient humidity making things exceptionally hard on your tarantula. Use fluorescent, or better, no lights at all. I do not recall seeing any lights in any wild tarantula burrows, and most of them appear to be nocturnal creatures, so the lights may be a disturbance. 

What do they eat?

Most tarantulas thrive on a diet of live foods typically available at pet stores. These include, but are not necessarily limited to, crickets, mealworms, wax worms, mouse pups (pinkie mice), and cockroaches. All of these are commonly bred to feed tarantulas. Any uneaten food items should be promptly removed, as crickets and mealworms, in particular, can turn the tables and kill a tarantula that is in the molting process or other weakened state. Wild caught insects are not the same as store bought. They can come complete with a pesticide and parasite load. Be careful where you get your foods from if you value your tarantulas! 

How often do they eat?

When they feel like it, plain and simple. Try to offer them some every day and remove what is uneaten. Eventually, you will come to understand the pattern of the individual tarantula. Unlike dogs and cats, they do not require 'X cups per day' of food. In fact, some species or individuals may fast for six months at a time, being none the worst for wear at the end of it. Rather than agonize and worry over it, consider it a time of savings on food that can then be put toward purchasing more tarantulas. As long as the abdomen is healthily plump, you likely have nothing more than an impending molt on your hands. 

Shelter, temperature, water, food. That's about all there is to it on a basic level.