Basic rule of thumb: you gotta hit that clit, but not too soon, and not to hard, and not directly ... at least not until the very end.
What a girl likes between the thighs varies from girl to girl. I've had girls that couldn't stand direct clit action, some that hated kisses on their lips, some that needs that little pounded like it was minute steak.
You've got to - pardon the expression - feel your way around. Try something, see how she reacts, but it's hard to go wrong with a gentle approach - kisses and finger strokes up the inner thighs, and over her pussy lips. Start licking her gently, moving from bottom to top (not that bottom!), inserting your tongue between her lips, just the tip, then the more and more as you move upwards. Take your time, keep heading up towards the treasure.
You'll be able to tell pretty quickly how its working ... moans, pelvic movement, increased wetness. When you get to her clit DON'T attack it. Go around it, gently licking in circles , passing your tongue over the top of it very now and again. The clit wil be rock hard if you are hitting the spots.
Then, go for some indirect pressure, running your tongue from its base upwards over it, then circle round and repeat. Increase the pressure as she increases her reaction to it.
Now's a good time to have a finger or two inside her two - again, go slow, sliding in with the same rhythm as your tongue and when you are deep enough, use a 'come here' motion, sliding in, curling your finger upwards to stroke the upper walls of her pussy, doubling the rhythm of your tongue on her clit.
As she approaches orgasm resist the temptation to rush her by upping the pace or pressure, but a little increase in tempo and vigor won't hurt and will also give you a great indicator of what she likes/needs for oral satisfaction.
Mix it up a bit with the tongue: flickers, licks - some long and deep, others shallow and passing, maybe a few sucks directly over the clit (one girl I was dating exploded at this point).
Just don't rush, don't pressure yourself, have fun and don't be afraid to ask her what she likes.
Good luck!
