I agree with Hung... trial and error, my friend. Its lots of fun! Every woman is unique, just like all of them, and some respond to different tactics and techniques while others don't. I have never had to jackhammer a clit to make a girl cum. Its just not necessary. Also, something that worked before might not work again, as moods, scents, and desires and needs change constantly.
Above all, communication is the keystone. Talk with your partner, ask what she likes. The girl may appreciate the gesture and actually open up more to you... but never expect a woman to give away all of her secrets, cuz that's just not gonna happen.
Good luck to ya man! When you practice... see if u can do two-a-days! ;-)