i often heard and read from women that the best oral sex they get is from other women. I guess is because they exactly now what to do and where to do it (like in the very instructive post from Brandye,
thanks for the tip!).
But i wonder ... could it be that a blow job from a man could is better than one from a woman? Hmm, i'm not sure if want to say that i'm curious LOL.
And for the original question, well, i always listen to my g/f, if the sounds of pleasure are getting louder it means i'm doing something good, if not, i move to some other place.