man, if you really want to know how to do it, just type "female ejaculation" into a search engine. I did that when i was 14 (it was one of the first things i ever looked up on the internet).
All the info you need is there. Though, in simple terms, what you do is this..
..stimulate the G spot. Now, this is located inside the vagina. About an inch & a half in. You should feel the upper wall & this 'spot' should feel different from the rest. Now gently stroke that spot with your fingers. Do a 'come here' type motion with your fingers against this spot. Then, as you progress, get faster, harder & apply more pressure.
I've heard that the most effective way of doing this is to use you middle finger & your wedding ring finger & do a kinda 'spiderman' action with your fingers. This is because theres more strength in those fingers, thus, you can stimulate it more.
This should be done ASWELL as the usual foreplay, including plenty of ****oral stimulatation.
Physically, theres no reason why any woman can't squirt. But, for those that don't, it's usually pychological.
Keep trying. Even if she doesn't 'squirt' she'll most likely have an amazing orgasm anyway.. so you can't lose!