This is how you boys become men- while licking your girl's clitoris, stick your middle finger in her kooter and apply pressure on her G-spot (about 2 1/2 to 3" in) or until she's says "OH...!", sometimes curving your finger may be necessary, and then you keep licking and having your girl hump your finger until she says something along the lines of OH SHIT! or OH MY GOD! This is your indication that you will have achieved a multiple orgasm
Here I am, 20 years old, and making my fiance, Moira (who's 24 years old) moan and scream her head off, while her kooter cums on my finger MULTIPLE times, thus achieving a mulitple orgasm, and consistantly. Moira has a multiple orgasm every time I go down on her.