A tarantula is the ideal pet for some people. With a little bit of background knowledge, you can have a great pet that is fairly easy to take care of and that is very awesome to watch. You have a lot of different options for choosing a tarantula friend, but the general care is very similar. You will want to find out more specific information for certain species such as their humidity needs, final size, and food choices (which may be different for larger spiders). However, you can get started with the care information here.
Housing. The first step of caring for any pet is to meet its housing needs. With a tarantula, you will need a glass or plastic enclosure. This could be a tank, an aquarium, or even a plastic pet keeper or critter keeper. You will want to make sure there is lots of ventilation, but that your ventilation holes aren't big enough for your spider to crawl through (they can get through spaces that seem much too small). It is better to be safe then sorry, so cover large holes and spaces with screen (you can buy a roll of soft screen at most hardware stores). This will prevent the spider from escaping without cutting down on air and ventilation.
Substrate. Your spider will need a good substrate for the bottom. There are many options and it is really up to you. In fact, you may have to try a few different things before you find the one that is right for you and your spider. For most spiders (non-burrowing tarantulas), vermiculite is suitable. You can mix in cocoa fibers, chipped bark, and/or peat moss. There are other options as well. You will want to avoid potting soil and bringing in anything from outside. Potting soil tends to mold quickly and outside plant and animal materials can have mites, molds, and other pests which can be harmful. You will want about one to two inches of substrate for your tarantulas unless you are hoping that your burrowing tarantula will burrow, then it will need to be deeper and should be something more suitable to dig in than vermiculite.
Hiding spots and decorations. You can add a number of decorations that can serve as nice things to look at in the cage and also as good hiding spots. Coconut shells or parts of shells, broken clay pots, fake plants, and fake logs can all make great hiding spots and great things to decorate your cage with. If you find your spider doesn't like something or that they hide too much, you can decrease the number of things in the cage. Or add things as you desire.
Water. While food is something tarantulas can go long periods of time without, water is important. All tarantulas should have a small narrow dish of water that is smaller then the radius of their legs (if possible since some babies will be smaller then this). You will need to keep fresh water available. Sponges are bad watering options for tarantulas, but some are sold for that purpose. Some tarantulas have higher humidity needs as well and they will need to be sprayed down or have their ventilation covered with a moist cloth. If your spider has higher humidity needs, then you should also get a humidity gauge for the side of your tank.
Food. Most tarantulas can live on crickets of a size appropriate to them. However, you can get creative with their food. Wingless fruit flies are an option as are mealworms (make sure they don't burrow or you make find the mealworm eating your tarantula during moulting time). Some say that termites are a good option, too, though it's best to avoid wild food unless you know it doesn't contain pesticides. A larger tarantula will also enjoy a pinkie (baby mouse).
Moulting. It is important to know that as your tarantula grows, it will moult its skin. Most spider owners notice something is "wrong" when the tarantula stops eating for several days. It is a good idea to get out all food that is in the cage when your tarantula stops eating it. Your tarantula is most vulnerable during its moulting process and you touching it could prove fatal, as well as it being attacked by food such as live crickets or mealworms. To moult, it will lay on its back. This could take several hours or even overnight. After it is done, there will be a tarantula skin and a tarantula. You can keep the skin or dispose of it. This is how your tarantula will grow and get larger. Hold off on feeding it for a few days. Your tarantula won't starve and this will protect its delicate skin from defensive food. Resume feeding after three to five days.
Special needs. It should be noted that some species of tarantula have special needs. They may need it to be warmer in their cage than it is in your house (especially true if you live in a cold winter climate). Others need high humidity. Others need special food, especially if you are getting a very young spider. It might need you to cut up worms or crickets or you might have to deal with pinhead crickets (babies that are very small). Be aware that these are some needs you may have to meet depending on the species you choose. It is a good idea to read a care sheet first and/or talk to some people on spider or exotic animal message boards.
Most tarantulas are easy to care for and make good pets. None of them should be handled regularly or often and all can bite (though a tarantula bite isn't fatal). You should watch kids around them and teach them to respect the tarantula. However, even with these issues, these are fun pets to watch and can make for a very enjoyable pastime. Some great species to start with include: Chilean Rose, Entre Rios, Curly Hair, Red Rump, and White Collar tarantulas. Others may be just fine for you--do your research and you will figure out the kind that you want the most. You can mail order them from breeders online or sometimes find them at local pet stores. It should be noted that if you are having your tarantula mailed to you, you should overnight it for safety reasons. Now you have the knowledge that it takes to care for your tarantula--have fun and enjoy!