Women have two very important points for sexual stimulation; the clitoris and the G-spot.

Location of the G-spot: As can be seen in the female g spot diagram here, the Grafenberg or "G" spot is located inside the front wall of the vagina. You can find the female g-spot location halfway between the back of the pubic bone and the front of the cervix, along the course of the urethra and the bladder where it connects with the urethra. The size and exact location will vary slightly with each woman.For some women hitting the g spot can bring deep and intense orgasms that differ from a clitoral orgasm. For other women stimulating the area called the g spot just makes them feel like they have to pee.G-Spot orgasms are triggered by a brief, vigorous, application of rhythmical friction. The desired friction is usually achieved when intercourse is practiced from behind or in the doggy style sex position. (See Image below)
Locate the G-Spot with your finger, the G-Spot will feel like a small bean, and when properly stimulated, may swell to the size of a dime or even as large as a quarter. Some women have large spots, just as some women have large breasts, and some men have large penises.
You will find the G-Spot located deep within the vaginal wall.
Firm controlled, pressure is needed to reach the G-Spot in its non-stimulated state. Stroking this area with a firm, masterful touch, she will experience twinges of contractions in her uterus. As she approaches the point of orgasm, if this is her first time having one this way, she may get a 'full-bladder" feeling. This happens because of the prolonged intensity of the orgasm. The clear, whitish fluid from her G-Spot ejaculation will be different from that achieved through clitoral stimulation.Researchers have attempted to build on the claim that G-spot stimulation leads to female ejaculation, hypothesizing that non-urine female ejaculate originated from the female paraurethral glands, or Skene's gland.
The best way for a partner to discover her G-Spot.
You are more likely to find the G Spot if the woman is already well aroused, and using fingers are generally more effective than a penis.
1. Ask her to lie on her belly, legs apart, and hips rotated slightly upwards.
2. Insert two fingers (palm down) and carefully explore the front wall of her vagina with a firm touch.

Position one
Guide her on to her hands and knees, with her buttocks raised and her head down. Kneel behind her and grasp her by her waist. As you penetrate her vagina in this position the head of your penis will hit her G-Spot automatically.
Position two
Guide her on to her back, raising her buttocks and lower back. As you mount her, gently bend her legs so that her knees touch her breasts. Now lovingly thump her G-Spot until she is an orgasmic mess.
Position three
Lie on your back, with your legs extended. Have your lady straddle you, with her knees positioned outside your legs, she will be facing your feet with her back turned to you. In this unique position, your penis will easily hit her G-Spot.
Female Ejaculation
The G Spot is said to be linked with female ejaculation where women produce fluid on climaxing similiar to males except the ejaculate is usually a clear watery fluid that is not urine.