hm, best advice is this:
Not many girls can actually have a REAL oragasm.
-The best ways for trying to get a girl to oragasm are as follow:
Find her g-spot... best to look on google to show where but if you can't. (It's found by placing your palm face up usually put your middle finger in and curl it up.
Rub her clitoris... All the major never-ending give extreme pleasure to a woman
Sometimes girl's may prefer using your tongue, but if you want her to orgasm, if she can, it's easier to use what you can do it faster with (hands, tongue, other)
Make suer though you remember that not all girl's CAN orgasm, it's very rare and most usually just involve them getting aroused enough to the point of wetting themselves - where it drips, not squirts out (fake orgasm).
Hope that helps