An orgasm isn't that different from an electrical capacitor, building up arousal until a firing threshold is reached. Stop and she'll return to her baseline—and you'll start from scratch.
Here's how to create sparks every time.
Stage 1: She Becomes Aroused
Her body starts to lubricate the vaginal canal and inner labia. The brain orders the release of the chemical vasoactive intestinal peptide, which increases blood flow to the pelvic area, swelling the inner and outer labia, and causing her to feel the sexual tension.
Stage 2: Her Body Unwinds
The parts of her brain that process fear and anxiety start to relax and the uterus tips upward, making the vagina longer. (The process is called "tenting.") The clitoris swells, as does the spongy tissue around the urethra, which is why some women feel as if they have to pee when aroused. Indirect touching of the clitoris will make her crave direct stimulation, adding fuel to her sexual-feedback loop. (And let's not forget about the guy. Here are 8 Ways to Make YOUR Orgasm Better!)
Stage 3: Her Vital Signs Increase
As her heart rate and breathing speed up, pumping more blood to her extremities, the color of the labia deepens, and her clitoris—ultrasensitive at this point—extends, fully engorged, awaiting contact with your penis. Slow, steady stimulation that builds rhythmically will help coax her body toward the threshold to climax. The more anticipation she feels, the better she'll respond. (Don't know where to start? Consider these 45 Sex Positions Every Couple Should Try.)
Stage 4: She Nears Her Threshold
The conscious part of her brain, drowning in neuro-transmitters, enters a trancelike state. Just prior to orgasm, the subconscious part—which also handles things like breathing and heartbeat—signals a vaginal nerve to start muscular contractions. You may feel the outer third of her vagina "grabbing" at your penis, but her arousal may fade and she will still revert to stage 1 if stimulation ceases or changes. (To keep her on the path to pleasure, study these 10 Lessons about the Female Orgasm.)
Stage 5: She Reaches Orgasm
The orgasmic stage—with rhythmic or sporadic contractions in the vagina, uterus, and anus—typically lasts 10 to 60 seconds. At this point, some women prefer more intense stimulation that matches their orgasmic response. The chemical oxytocin is released in the brain, promoting a feeling of closeness, according to some research—which could explain why she wants to cuddle after sex.
Stage 6: Her Rest Period Begins
Unlike men, some women can have multiple orgasms without experiencing a refractory period after each one. Without stimulation, however, they will return to a base-line level of arousal. Contractions stop, the uterus lowers, and the clitoris goes back in its shell. Heart rate and breathing slow, and bloodflow returns to normal. The clitoris will probably be too sensitive for direct stimulation, but other parts of her body will be yearning for attention. (Or get some rest and be ready for tomorrow with these 7 Ways to Have Kinkier Sex Tonight.)