If you want to give your girlfriend maximal pleasure you have to ask her for instructions. Girls all masturbate in a different way: preferences differ greatly. She is the only one who can tell you what feels good and what doesn’t.
1.      Sit, stand or lie down behind your lover, with your arms around her. Your hands are in the same position as hers when she masturbates.
2.      Let her stroke her body herself and put your hands on hers. Remember where she touches herself and what kind of movements she makes. Does she speed up or slow down when she gets excited? Is there a certain rhythm? How firm are her strokes? Are her fingers on the clitoris itself or does she stimulate it indirectly?
3.      If you think you have a good grasp of what she is doing change the position of your hands, letting her hand guide yours.
4.      Try different things and ask her what she likes best, for instance stroking her inner lips firmly and lightly and asking which way she prefers. You won’t look foolish for asking. It only shows you know no two girls are alike and that you want to become a good lover.