Written by Emily Nagoski, Ph.D.
You rub it.
How exactly you do that depends on how you're wired, and you can only figure that out through trial and error. Here I'll give you some basic techniques that work for various women. Remember, with all manual penetration, the fingernails should be short, well groomed, and very, very clean. I also recommend latex or polyurethane gloves, not just because of their obvious infection prevention benefits but because many women prefer the smooth texture of the glove over the rough texture of a hand. If you can't get used to the idea of a rubber glove during sex, that's fine, but don't knock it before you it. You might be surprised how good it feels.
Pressure: You might find that the best stimulation for you is just steady, direct pressure. Adding clitoral stimulation is a simple way to increase the intensity of any self-pleasuring experience. Start with a high level of arousal generated by clitoral stimulation, use a little lube around the mouth of the vagina if you like, and insert a finger or object about two inches into the vagina and press up, against that front wall of the vagina.
Come Here: With a finger or two or three inserted with the fingertips just beyond that special area, pressing up against that anterior wall, bend your fingers in a "come here" motion. This provides pressure and motion against the G-spot and is the standard recommended stimulation type. Make sure your fingernails are short, smooth, and clean!!
Tapping: With a finger pressing dead against the center of your G-spot, tap your finger rhythmically against the area. It's not really wiggling because it doesn't matter much about stimulating the posterior wall of the vagina. Don't think back and forth or side to side, just think tap. You might like hard and slow, you might like light and fast, you might like hard and fast or light and slow. Try many variations and see how your body responds.
Glass: Using a glass or acrylic or other very hard dildo, when you are already very aroused, rub the toy against your G-spot. Play with different angles of penetration and different speeds. Remember the G-spot is right at the entrance of the vagina, no more than about three inches in, so you're not looking for deep penetration, but intense pressure on the G-spot. Your body may like very small, slow movements over the surface of the G-spot, or it might like very fast movement. Different women need different kinds of stimulation, so try a variety of things to learn what your body likes.
Buzz: Using a penetration-style vibrator, tilt the shaft so it angles up toward your abdomen as you insert it. The vibrator will buzz directly in contact with the G-spot. Dual vibrators are convenient for this kind of stimulation because they work the clit at the same time. However, until you're very familiar with G-spot stimulation, it might help to avoid too much direct clitoral stimulation at the same time, since that sensation might overwhelm the G-spot stimulation. Clitoral stimulation and orgasms are fantastic, but they are a distraction from G-spot stuff. Once you've got the hang of the G-spot stuff, then you can integrate G-spot and clitoral stimulation simultaneously.
All of these techniques can be combined with both clitoral and anal stimulation for more intense and complex experiences, and remember you should always be aroused before you try anything with penetration. Once you're very aroused, start with penetration slowly and increase the stimulation as you become more aroused. Take your time, the build up to G-spot orgasms can be long and intense (as in, an hour or more). Orgasm alone is not the goal; you can enjoy an intense and pleasurable new experience that is not necessarily orgasm but is definitely a nice way to pass the time.
Also, all of these techniques can be done in multiple positions. You might find it most comfortable to try these while lying on your back, which allows you to put pressure just above your pubic bone, which helps many women locate the G-spot. You also might prefer lying on your belly, which makes reaching the right angle easier. Another position to try is kneeling, sitting on your heels. With your torso upright, you can have more control over the movement of your hips against the finger or toy.