There really is no science to it. Some chameleons are just more comfortable doing it than others. My advice would be to not give up and just keep trying. hoepfully the more he gets to know you the more he will trust you. You could try tongs and see if he would go for that and then graduate into using your hand instead. Try using a worm that wiggles alot to get his attention. Crickets don't move much! Just an idea...