OK, I think you mixed up a few things.
There's a whole bunch of erogeneus zones, one of the most potent ones being the clitoris. The G-spot, on the other hand, is a mythical, or not so mythical, depending on who you ask, THE erogeneus zone. THE zone, meaning the most potent one. It has nothing to do with the clitoris, and it's actually inside, not on the surface, like the clitoris. It's a patch of rougher skin, which is how you're supposed to recognise it. The lady in question, of course, doesn't need tactile cues to recognise it.
There's also a matter of certain positions that allow easier access to the G-spot, but now I'll shut up before I turn into Dr. Ruth.
Incidentally, the male G-spot is supposed to be the prostate, right? lol I know more about female anatomy then my own.
Keeps my girlfriend happy, though...