This is how I introduced my now ex-girlfriend to masturbation.
We dated for 3 years during college. For the first six months, we did alot of oral and hand sex on eachother. She was a virgin. We started sleeping together after six months, and it was great. To add variety, we would often go back to oral or hand...especially me going down on her, she loved it. We experimented a little bit, but not too much. I fingered her asshole a few times, but we didn't do to much 'daring stuff.'
She loved being teased. I would get her undressed to her panties, and run my hands all over her body. I would tease her nipples, slide my fingers across her small ass, and across her stomach, and around her panty line. Eventually, I would ever so lightly touch her pussy through her panties, teasing her and driving her mad. I'd take off her panties, and continue to just brush her pussy, until she literally squirmed from being teased. I would then insert a finger or two, or go down. This would often go on for 30 minutes or more before we actually had sex.
On one of these nights, I decided to see if I could get her to touch herself. I've masturbated for years, and always dreamed of watching a woman do it. I teased her like mad, to the point where she would try to take my hand and guide it to her pussy. I evaded, and moved her hand there instead. She tentitively touched her clit, and sighed in pleasure. She touched it a bit more, before grabbing my hand, and we both rubbed her clit until she came.
A few months later, I decided to try again. I teased her like crazy, as usual, and again wouldn't let her pull my hand to her pussy, moving hers there instead. I lightly took her hand, and guided her pointer finger inside her pussy. I kept my hand nearby, so she didn't feel to wierd, but she sat back and fingered herself to orgasam. Afterword, she looked at me and sort of laughed, and said 'I just fingered myself!' I licked the cum off her finger, which she seemed to like, then went down on her for a bit before I couldn't wait anymore, and slid inside her now very wet pussy.
We broke up only a month or so later, so I never got to explore further with her, or find out if she ever tried it on her own. My new girlfriend doesn't seem to want to touch herself, though I got her a small vibrator for x-mas that she loves for me to use on her, and she has thought about taking home. Perhaps there will be a new story there in the future.