The natural habits of chameleons make them tricky to care for - they are arboreal, living exclusively in trees. They are solitary, and easily stressed. As a result, they need a cage with ample foliage for climbing and privacy. The enclosure must be quite large - for the larger chameleons a minimum of 3 feet by 3 feet by 4 feet tall should be provided - but the more space the better. Ample ventilation is required, and a cage screened on three sides is best, with poly mesh or vinyl coated wire preferred to prevent injury due to toes becoming caught. Lots of branches of various diameters need to be provided for climbing and the bulk of the cage space should be filled with branches or live foliage. Ensure that the plants are not toxic, as the chameleon may sample the foliage. Some enthusiasts recommend avoiding ficus plants as well. Substrate made up of small particles (gravel, sand, bark, moss) should be avoided to prevent the chameleon from accidentally eating it while catching prey. Several basking areas of various temperatures must also be provided, ranging from the upper limit of the species temperature preference to the loser end of the range, to allow the chameleons to thermoregulate. Jackson's chameleons do well at lower temperatures, but panther and veiled chameleons prefer warmer temperatures. Readers are referred to the sites and care sheets listed below for specific temperature and humidity requirements for the different species.
Chameleons do best with access to natural sunlight, but this is not feasible as a sole source of UV radiation for most owners. Incandescent and full spectrum (UV) fluorescent lighting is necessary. In addition, allowing some exposure to natural sunlight through an open window (glass filters out nearly all of the necessary UV radiation) will help keep chameleons happy and healthy (or placing the chameleon outdoors if the weather is appropriate, providing adequate shade to prevent overheating).
Chameleons get their water from droplets on leaves - as a rule they will not take water from a dish. Adequate water intake must be provided either through a drip system or by misting the enclosure at least twice daily. Drip systems can be purchased or fashioned from a water container with a pinhole placed on top of the cage, or even by placing ice cubes on top of the cage to melt slowly and drip into the cage. If a drip system is used, keep the watering location consistent so the chameleon knows where to find water. Misting will also help keep the humidity levels up. If a drip system is used, the excess water should be collected and removed though, to prevent the humidity from getting to high.
Chameleons seem to do best on a variety of insect foods. Try to feed as many types of insects as possible. Crickets, meal worms, super worms, wax worms, wax moths, non infesting roaches are all good items to feed. Prey food should be gut loaded with nutritious foods (leafy greens, vegetables, fruit) prior to feeding, and should be dusted with a calcium and vitamin D supplement. Chameleons may be susceptible to overdosing with vitamin A (hypervitaminosis A) so supplements must be balanced carefully. Again, the care sheets below cover details of supplementation. Keep in mind that egg laying females will need extra calcium supplies. Also, some nutritious leafy green (avoid spinach, lettuce, and cabbage) and other vegetables and fruits can be offered in small amounts as chameleons will occasionally sample these.
Chameleons are easily stressed, so cages should be placed in low traffic areas (a quiet room is ideal), and barriers (e.g. lots of foliage in the cage) between the chameleon and household activity should be provided. Avoid handling the chameleon and when observing the chameleon move slowly. They are fascinating and amazing, but need some special considerations to keep them stress free and healthy.
Here are some good resources for chameleon information: