I've watched two "how to" videos, and the one technique that they both recommend (and has never failed for my partners over the years) is this:
begin with giving her oral sex (light clitoral stimulation at first, building up to more and more intense) until she is squirming and very wet, then add penetration with a finger or two (fingers curled slighly upward beneath the pubic mound towards the alleged g-spot at 11 o'clock, rythmically with her movements).
One video I saw was an alleged academic "sex expert," and one was the porn star Shane explaining and demonstrating. I liked the Shane video better
Here's the catch: having been with a few women in my time, I have learned that some women can come 10 times in 5 minutes with regular old sex, while others require a good 30-45 minutes of oral + manual stimulation to get there. Men, when we are young, tend to not have the patience and/or consideration to figure that out until a good woman or two teaches us, and it kind of gives you a neck-ache after 30 minutes. But a man who appreciates the wonderful booty his mate shares will learn to love it, neck-ache notwithstanding.