Mine are set to drip quickly, 1-3 drips a second, in the early morning, until about a litre has run through (less than 15 minutes). This is when they prefer to do most of their drinking. Late morning i refill slow the drip rate to about 1 drip every few seconds or so, and that lasts longer. In the mid afternoon i fill the drippers again.
How often you run your drippers will depend on the type of chameleon, its age, how hot/humid it is there, how much you mist, the type of prey you offer and what you feed that prey.