For most men, I would suggest playing with his balls...
My SO doesn't trust me around his balls due to my deeply buried CBT/castration fantasies. I'd never actually act it out, but I digress... Anyway, without handling any of his other "goodies", you can try varying the suction- some girls just bob their heads up and Down, try actually sucking with different pressures. Vary the tightness of your lips according to how he responds. Use your hands and your whole body, really get into it and rub your chest against him, hump his leg
, etc. My, well, HIS favorite move is when I look into his eyes and moan. Not only does this show enthusiasm, the slight vibration can be a turn on. Or, try holding a vibrator against your chin as youre blowing him for a really intense feeling.