MMM-HMMM!! I eat pussy as I like mine to be eaten (then adjust based on her feedback): I usually start with some slow, firm kisses on her inner thighs, moving my way toward her pussy, nuzzling my face and hair against her (don't skimp on the amount of time spent with this - make her really want it!). Then long, slow licks - full tongue! - along the outter folds, sucking gently until I work my way against her inner lips, separating them with my tongue and continuing to suck and lick them. I always start with doing everything slowly and gently, taking my time, until I feel her start to move her hips and push her pussy against my face. If you really pay attention you should be able to detect a difference between the initial movements and those she makes as she starts to head toward orgasm. Then my licking becomes firmer and a bit quicker until I decide to finally take her clit between my lips and stroke it with my tongue as I suck it softly. By this time I'm probably fucking her with a finger or two and allowing her to let me know (usually with her body language but sometimes verbally) what, exactly, she wants.
Personally, I think the most important thing is that you WANT to do it and are enjoying it. As I told someone once, when you do it for yourself it's always better for me! Sometimes the reason a woman can't cum via oral sex is because she's so concerned that the guy isn't enjoying it that she can't relax and get into it. So enjoy the journey and don't get hung up on making her cum.