Reach up to you earlobe, and behind it. There's a little soft bit of skin that isn't actually on the earlobe, but on the neck (?) behind it, it's like the earlobe is shielding that part
My girlfriend pokes out her tongue, and hardens it (I can't think of a good way to describe it). Then she pokes and licks that area and it drives me wild!
Hrmm, where else? Light scratching/tickling of my nuts is a great feeling and she knows it
She also plays with my hair and scratches my head a bit, it's not exactly a sexual turn on, but it feels really nice. Especially when we're just sitting around watching TV or something and she just does it without concentrating