G-spot
For many women, it's a highly sensitive, highly erotic area that provides hours of pleasure. For others it's a knobbly bit that, when touched too much, creates an overwhelming sensation of needing a wee. Some women can't feel any sensation at all while others don't seem to have one at all.
There are a number of different theories about what the G-spot or area actually is. One view is that it is an area of prostatic tissue similar to the male prostate. The absence of the Y chromosome in the developing female fetus deposits the cells in a similar location and voila - the G-spot. Complete with a similar type of sensitivity to the male prostate.
Another expert agrees with the prostate theory but expands it to say that this is not the only reason for sensitivity. He points to the clitoris and the urethra as other sources of pleasure, both of which can be stimulated via the front wall of the vagina.

Say what you'd like to try
Talking about what you like and dislike has several benefits. Not only can simply talking about sex add to your excitmement, but the more you talk, the more relaxed and confident you'll be with your partner.

Be honest, positive and demonstrative
If you're going to say what you'd like and ask what your partner wants, there are three important points to keep in mind.
Be positive. Don't tell your partner they're terrible in bed. Remember something they did that you really liked and say, "When you did that, I really..." They'll get the message.
Be honest. There's no point in faking it or saying you like something you don't, because that gives your partner no incentive and no guidance to do better.
Be demonstrative.