um, LJ, I'm not sure if all men will agree with the nibbling thing! As far as I've learned, teeth are baaaad- very, very bad. I am hesitant to even try nibbling.
My thoughts on oral sex:
1)We know you shake the urine off of your penis and let it dry there. If you want it in someone's mouth, WASH it.
2)Balls sweat profusely and when it gets damp down there, it gets smelly real fast. WASH 'em.
3)Silent hit the "head" on the nail. Everyone is different, so you're better off asking "how do you like it?" Don't go around nibbling everyone
And yes, rhythmn and supression of the gag reflex are important.