Like others have said....they are very though to keep healthy...I really hope this is not your first rep.
They need rather experienced keepers to be healthy...
But if you are going to get one reguardless...here's some info...
The usually do not like to be held and should be kept solitary, they only do well when they are breeding, any other time, there should only be one in a cage...they Need LOTS of space and hiumidity...
I dont want to write a novel, so here are some sites to help...
http://www.martinsreptiles.co.uk/ukchams/calyptratus_caresheet.htm
http://www.geocities.com/chameleoncreatures/veiled.html
http://oror.essortment.com/chameleonscare_radb.htm
You can find tons of sites with info for you...And PLEASE find a good Reptile Vet befor you get one...talking to a vet about it is a great idea also...before you get one...they are no joke, one of the hardest reptiles to take care of...
Hope this helps...GOOD LUCK!!!