First let me say that you are crossing into dangerous territory! You are already doing a great job by giving her an orgasm. Not all women have orgasms all the time so you are ahead of the curve.
But men seem to have this little voice in their head that says "If I can make her come once, I can do it twice." "If I can make her come twice, I can make her have a female ejaculation". And means' magazines are filled with this stuff. The problem with that is you are setting yourself up to fail.
Here are the facts: Not all women are multiple orgasmic. They never will be. Not all women are able to have a female ejaculation (or squirt). That is another fact. I know the idea of her head exploding from an orgasm is the greatest thought in the world but orgasm are different for a woman then they are for a man.
For a woman, an orgasm is completely letting go to trust the man she is with. That's why some women will never have an orgasm. Because they can't let go, regardless of the man and his love for her.
So, for your girlfriend to have a "better" orgasm, that isn't dependent on you, it's dependant on her. I say this cause I am speaking from not only research but personal experience. I hope I don't sound graphic here but I have gone from having one mediocre orgasm to being able to have as many as 10 orgasms and being able to "squirt". And let me personally tell you, it isn't as great as you think. One orgasm is just as satisfying as several. I know that sounds crazy but it's true. But my point is, to get to that point, it has taken me years of learning to relax and trust. It has little to do with the man's technique. I will orgasm more and harder for the man I trust then some guy how has 47 positions he can pull out.
I know this kills to hear cause it isn't a skill I'm telling you but the best way to give her more intense and satisfying orgasms is to be a great guy out of bed. If you listen to her, give her kisses, telling her that you care about her, and show yourself trust worthy, her orgasms will be insane. A man who can help a woman relax and trust him in bed will truly give her better orgasms.
Women aren't as freely sexual as men. We are taught not to be. So while her performing a great blowjob on you may be the best thing ever, allowing her to completely trust you and know that you are sexually taking care of her, will blow her mind like the most skilled blowjob you've ever received. Giving a woman a safe place to be completely sexually open and free is the best thing ever.
OK so maybe I will give a tip or two. :) To acheive that freedom for her, ask her about her fantasies and never ridicule them. Have her lay against you and take your hands and let her show you where she wants to be touched. These things make a woman feel like you aren't going to go "Oh how slutty!" cause remember if a woman likes sex she is made to feel that she is bad. She wants to be as free as you are. Give her a safe place to do that.