What do I do with my hands when I'm kissing my boyfriend?

Hands around his neck is perfect. no need to do anything else

Oh! the "art" of making out.... the guys that I've dated loved that my hands would start to play with their hair, massage their scalp (the idea is to relax them and to make them enjoy the make out session), then slide your hands to their ears and just play with the earlobe, the trick is to do it slowly, this will relax and enhance their feelings, then slide to their neck but really reach for the back of their neck and again massage, if you wish you ( this is a bit more risky and will turn some guys on), slide your hands under his chest and caress it slowly. If you want another idea instead of the chest, go for the back or at least the shoulders, just caress them ( works better if he's wearing short sleeves). Oh one last thing different pressures and speed of the strokes are encouraged, the more variety the better!

Hope it helps!