Not all women can achieve an orgasm. Most women who can, can only have it through clitorial stimulation, most women can not have a orgams from vaginal intercourse.
The best way is to masterbate by yourself. Try to find out what feels the best alone. Try to orgasm when no one else is around. Then take all you have learned and talk to your partner about it, give him instruction on where to touch. Use toys if you have to.
My wife can not have a orgasm during vaginal sex, she needs clitorial stimulation. So I will perform oral sex on her until she does. From time to time we will use toys during oral sex and sometimes during intercourse if she wants to have an orgasm then.
But like I said you need to try to do it yourself first and then be a teacher. And I also encourage oral sex.
I have the same problems! I have been with my fiancee for 3 years and have never came with normal sex with him. Or any other guy in that matter. I was actually just thinking about posting this on here. Unfortunately I don't really have an answer. Last night was the first time I got to orgasm during sex with him, but that was with some help from a vibrator lol. I hate that I can't orgasm during sex! Its frustrating and my fiancee also thinks its just because he is incompetant. Sex is always good with him but I can never reach that point. Hopefully we get more answers! If you dont mind using a vibrator with him, then go for it...its totally worth it and its amazing!