Alrighty. The main thing to remember when trying to "tame" them is to leave them alone. Every time you force handle them or make them huff and puff, it sets you back. If you want a lizard that has no problem being handled and comes right up to you, you have to leave them alone for a while (4 months for the black throat). Once you can walk by the enclosure and they dont dart off and hide, you know you're making progress.
You'll have your hands full with that nile though lol.