turn your hand so your palm is facing up, and move your fingers in a "come here" motion, rubbing the fingertips on the front wall of her vagina.
This. Tried and tested method.
Everything you will read in this thread will mostly be on an individual by individual basis. You can turn a woman off easily, If you do something she doesn't like. Like sticking your finger in her arse. That and some women have sensitive clits and some can't get off by stimulating it.
Though one thing all women will respond to, is what is quoted above.
I've yet to meet a woman, who after 10mins of using the hooked finger technique hasn't orgasm'd
Think of the natural curve of a penis and angle 2/3 fingers the same way. Instead of going directly in straight, go in a slide them across the top of the vagina till you feel a slight dip(at this point your 2/3 fingers should be pretty much all the way in. Gently using the end of your two fingers, massage that spot just past the dip as you slide a little in an out each time. Not all the way out mind you, just an inch or two. The rest is just judging at whatever speed she responds too.
Some women like it slow then faster when they're nearing climax. Some like it slow all the way through. An there are the few who like a good finger blasting. You should easily be able to judge.
An if you're really brave, just ask her how fast or slow she wants it.
Too really rial her up, kiss her thighs and run your hands up her body. Hold one of her hands, while you finger fuck her with your other. You could make noises yourself, to show her how much you're enjoying pleasuring her. Things which the vast majority of women will respond to positively.
If that technique doesn't work, she probably used to be a man. Good luck.