TIPS.
1.) CLEANLINESS IS NEXT TO GODLINESS! Chameleons have evolved for an aboreal life in the trees. They are very suceptible to the dirty anerobic bacteria that accumulate on the ground. Don't let poop or dead feeders accumulate on the bottom of your cage. In short keep the bottom of your enclosure clean.
2.) DON'T CONFUSE CHAMELEONS NEED FOR GOOD HYDRATION WITH EXCESSIVE WETNESS/HUMIDITY. Chameleons need to be misted frequently to drink and hydrate their skin but just as important is that their enclosures dry out at times so bad bacteria(again refering to my first tip) aren't allowed to get out of control in constant damp conditions.
3.)UVB! UVB! UVB! Chameleons(at least the popular ones kepts as pets) need exposure to UVB light so their bodies can produce a vitamin(d3) that allows them to absorb calcium. Although many calcium products include vitamin d3 they can easily be overdosed and should be no substitute for UVB lighting. The standard UVB light that most chameleon keepers use is the linear(not coil/cfl) reptisun 5.0.
4.) GOOD NUTRITION. Chameleons will not thrive on a diet of poorly fed crickets like a lot of other reptiles will. Although crickets, dubia roaches, or silkworms can be used most of the time, variety is a key part of a chameleons diet. You should substitue their main diet with other inscets such as hornworms, superworms, phoenix worms, butterworms, or other non toxic insects.
JUST AS IMPORTANT AS VARIETY OF INSECTS IS GUTLOADING. Chameleons get a large part of their nutrition from the gut tract of the insects they eat which is why you should gutload all of your feeder insects, or feed your insects nutritious foods prior to feeding them to your chameleon. Good gut loading foods include Fresh greens(mustard greens, turnip greens, dandelion greens, ect...) Fresh fruit (papaya, oranges, kiwi, apple, blueberries ect...) and other vegies like sweet potatos, carrots and squash. Lastly with nutrition is the supplements. Calcium with out d3 should be LIGHTLY dusted on all feeders, calcium with d3 should be given twice a month and a good vitamin supplement such as herptivite should be given twice a month.
There is many more things that are important to chameleon keeping but those are the things I think people have the most difficulty with. GOOD LUCK!
I would highly advise finding a good chameleon vet before you buy your Cham and have a nice little saving account because no matter how good of care you take of these little guys sometimes things still happen. 
