Hi.
Basically, an orgasm is a pleasurable physical response to sexual stimulation, usually of the genitals, although some people have been known to orgasm by stimulating other parts of their bodies (or having them stimulated) or by simply thinking or dreaming about something sexual.
In both men and women, orgasms usually involve quick, involuntary and highly pleasurable contractions of the muscles in their lower pelvis--in women, specifically, the uterus and vagina. Many describe the sensation as radiating throughout their bodies as a whole. People often find that they have a feeling of euphoria or peace and/or sleepiness after an orgasm because of the endorphins released during the experience.
Considering all that, I don't think you'll have much trouble recognizing an orgasm when you experience it, but if you want some pointers as to whether you're heading in the right direction, here are some clues that there might be one on the way: hardening of the nipples; the swelling of the clitoris (the nerve filled "button" located just above the vagina); a moistening of the vagina; heavy breathing; and trembling.
As for how to have an orgasm, continue to explore your body until you know what brings you pleasure. Once you've found out how you like to be stimulated, keep doing it--the rest will fall into place.
And, if you would like to know more about orgasms, check out gURL's fast facts about orgasms.
Good luck!
