There's a lot to perfecting oral sex, but it will basically drill down to 3 things:

1. Communication. You both need to work on being comfortable talking about what's working and what isn't. Some women are very sensitive and you have to be very gentle, other's require stronger technique. Sometimes you'll use your whole mouth, other times just your tongue and the more you communicate about where and how much, the more confident you'll feel about pushing her over the edge.
2. Time. Women, in general, have a longer latency period than men. So grab your goggles and swim fins and don't come up for air until you see the whites of her eyes.
3. Body Language. Done right, reading her body language requires an almost laser-like focus on her pleasure. During this, work to try to read her body language, the ebb and flow of her excitement. Putting your hands on her is not just about bracing or holding, but feeling how her muscles tense and keeping her tense, but not so tense it hurts. Listening to her breathing and changing things so it stays high in her chest (or stops completely ). Reading her body language can be tough and it ties back to early communication.

As far as raw mechanics go, don't go to porn to see how it's done. Porn's all about camera angles and such. There are books though on Amazon and Google books that detail the simple mechanics, then apply your communication, time and reading body language and you'll have a happy partner.