I agree completely with what was said above. Chams like to be up high, especially in stressful situations. If for some reason you are dead set on wanting your cham to chill on your hand (I can't stop you, so...), just raise your hand above your head. Since your cham is in the highest possible position at the moment, she won't want to climb to your head. And you'll soon find out that raising your hand above your head will be quite the workout. She may look light, but soon you will swear she is heavier than a dumbbell. When this happens, it is best to put her back in her cage.
Chameleons really shouldn't be handled. Why put unneeded stress on your cham? No doubt she is beautiful, but she will thank you with her beautiful colors if you don't touch her.
I find complete bliss knowing my cham is "happy," so I just leave him alone and observe from a distance.