Before you can consider feeding the chameleon, remember that how you care for your food items will directly affect the chameleon.

Feeding crickets to your veiled chameleon: I usually put a small bit of calcium supplement and a small bit of mineral supplement in a plastic cup and shake them up. Then, I tap the toilet paper tubing on the side of the cup just a bit, until I have enough crickets in the bottom of the cup. Depending on the size of the crickets, is how you determine how many to feed the chameleon.
Juveniles and hatchlings should be fed more often than adults are, and female adults should be given more food and more supplementation than adult males. Hatchlings should be given pinhead crickets at least twice daily. Juveniles should be given slightly larger crickets, and can be introduced to plant matter and superworms, mealworms, etc. Adult veiled chameleons can be given a wide variety of food, including adult sized or smaller crickets, mealworms, superworms, all sorts of plant matter (discussed later), local insects (discussed later), and a few other food items.
Local insects: If you go this route, you really need to know what species of insects are toxic and what aren't in your area. Chameleons can eat moths, spiders, grasshoppers, crickets, etc. Also, beware of pesticides!! Never feed a veiled chameleon anything if there are pesticides being used in your neighborhood. I'm fortunate to live in an area where pesticides aren't really allowed.
Vegetable matter: As the Chameleon reaches full growth, it should be fed more plant matter. I keep a Pothos in the cage, and also tried an experiment with keeping the chameleon on a Ficus tree. They have been known to eat Pothos and Ficus leaves. Currently, I feed my veiled chameleon a mixture of vegetables. He eats:
Romaine lettuce
collard greens
mustard greens
turnip greens
kale
spinach
anything dark and leafy. do NOT feed them iceburg lettuce. There is no nutritional value in it at all!!! I also have been told to offer a small amount of fruit, but Karma has yet to show any interest in the fruit I offer him, and I refuse to offer him any banana, since my monkey skink had a problem with constipation due to too much banana in just one feeding.