Watch a movie with her (edit: tune in later for a post on "How to Get a Gurl 2 Watch a Movie wit yu!"
Make sure it's horror, or, as second best, comedy. But atrociously bad so you wont watch it.
Sit side by side on a couch
Get a blanket for you
Do not show a single hint of timidity: fling your arm around her
Tease her and tickle her, get her laughing
Progress to making out
Give her a massage
Give a good one
Then simply slide her hand onto your crotch
Whip it out
NEVER HESITATE. NEVER LOOK UNCERTAIN.
Unless she's a complete bish, she will slobber on your knob.