Find it with your fingers first, since you can feel much more than them. Do a bit of a google search, look at diagrams that point it out, and erad the descriptions of how it feels, then tell your gf you are looking for it, use one or two fingers along to front wall of her vagina not very far in when she is really aroused and you should be able to feel it, and she will be able to tell you when you have found it. It is important for her to be very wet, then you should be able to find it easily. And after you know where it is then you can try hitting it during sex, usually rear entry positions work better since you have to rub the front wall.

Using your hand, two fingers palm upwards fingertips curled up doing a come hither motion of the fingertips lightly pressing upwards, just go in one to two knuckles deep while she's lying on her back AFTER a clitoral orgasm. The G-Spot will feel somewhat spongy - like a squashed grape with goosebumps on it - the more aroused, the more goosebumps. Caressing here should help stimulate another orgasm. Remember to mover your entire hand in and out while caressing back and forth with the fingertips. Come hither is the key to success.

Remember how far you went in using your hand and place the head, just the head, of your penis there during intercourse. Position depends upon the curvature of your penis. If upward, then kneeling between her legs while she's on her back is best. If otherwise, you'll have to experiment a bit. Remember it is much the same as when using your hand, in and out using small pelvic thrusts while pressing upward against the G-Spot with the head of your penis. Use lubricant as needed - you want slide with some but not too much friction.

You will know when you have it by watching her reaction. Most women have HUGE orgasms from this kind of stimulation. By doing this after a clitoral orgasm, she will be primed and ready, as it were, for your further attentions - both relaxed and aroused.

It is likely that only about one woman in ten has had successful stimulation of the G-Spot. It is fun learning. It is usually addressed by hand as described in the other responses here. Stimulating it by penis is almost rare.

Start by reading arutha's and EvilEvilKitten's posts carefully. Now for hitting the G Spot during coitus it is important that you take into account the shape of your penis. If you have penis with a large head, an upwardly or downwardly curved penis you probably have an advantage.

When in man-on-top positions it is helpful to not insert the penis to the hilt as we are normally wont to do. Instead use short thrusts trying to keep the fleshy glans, especially the corona (edge) rubbing over the Gräffenberg spot which you hopefully have already located by following the advice of the two people who posted previously.

If you are able to lean back while inside her so that your heads are pointing in opposite directions this will stimulate the G spot. This is especially so if you have an upward curve. Also man sitting with the woman facing him on his lap or man kneeling with the woman on his lap or (if possible) man standing woman with legs wrapped around him are good face to face G spot positions.

Man sitting, woman on lap back to man is good. and doggy position is good also I imagine a downward curve is even better this way.

Because of the way men and women are built and the fact that most sexual positions do not place our respective pieces-parts in constant ongoing contact with our partner's in order to generate the necessary and desired friction, fingering the clitoris becomes an integral part of each of those positions. I'm not much in favor of trying to contact the G-spot with the penis. Why? "Thinkaboutit":
A. Intercourse requires a stroking action
B. The vagina increases in circumference when a woman is aroused
C. It is difficult for the penis to contact and constantly rub against the "spot".
D. Not all positions nor angles of the penis nor actions make it possible have the ongoing friction needed.

With these circumstances at play, better me thinks to work on the G-spot manually using a nimble and dexterous finger. Alternately, use a dildo or vibrator.

I say get good at finding it manually and see the responses from her. Let her figure what & where all is.

In the past; me being on top with him guiding my hips with his hands helps to keep a good rhythm. However, I find I have to keep him close to the anterior part of the belly...if I can get it right; he is patient, you get a good, slow and deliberate, rhythm going and while you are gently stroking with your penis. As another poster pointed out if she is sitting on top of you...try gently placing pressure on the external lower abdomen see how she responds while you are manually stroking the g-spot.

However, figure out how to stimulate it with fingers while she is aroused...after a few orgasms & a few times try using your penis. And do not be disappointed if it does not work ASAP. Many require getting used to the sensation and what they are feeling. You learn together.

As one who trains men in the finer nuances of sexual intercourse - IT CAN BE DONE. Not with all of them, I'll admit it, but with most, yes. While, having a large head and an upward curve is the best, whatever penis he's got he can be taught to use more effectively than most. As I have said, I'm not advocating drawing rings around his penis but if he needs it - get out the marker. Use different colors for the various depths if you think it would help. Gentlemen, it is a question of control, skill, and your desire to drive her crazy so she prefers you over any other lover. You tell me if that's not incentive enough. Loosen up that lower back, allow four hours for practice, grab the lubricant and lets go to 'school'.