Quads are my favorite site. Followed by calves. Never more than .5ml at a time. I burned out my glutes years ago from doing big injects of 1ml (that's a big inject to me).
I have best results alternating between pecs, shoulders, triceps, quads, calves. Biceps don't work too well for me. First the left then the right so that's 10 sites to alternate between so they can heal. I love the soreness but hate working out the muscle group until it's gone.