My $.02, born of bitter experience:
To begin with, ask a few simple questions: "What do you like? Fast or slow? Hard or soft?"
Every girl is different, so you just have to develop a basic repertoire and go through it until you hit a motion and rhythm that seem to be producing a positive response. When you do, stick with it.
Every girl is different than she was last time. I find very few girls that like the same thing every time. The value of variety cannot be overstated.
Teeth are not good for eating pussy. At all. Of all the things that women have asked me to do in the throes of passion, "bite my pussy" is not one of them. there is a difference between sucking on a clit and chewing on one. Fingers are a personal choice. I don't use mine unless asked. I'm happy to lend a finger, but my experience is that a girl will let you know if this is something she really wants.
One thing I have learned is to pay as much (if not more) attention to the "downstroke" as the "upstroke'. Don't eat pussy the way a dog drinks water! My observation is that for a good number of women, the "top side" (dorsal side?) of the clitoris is more sensitive than the underside.
One thing I have observed is that girls often don't seem to really know what they want. I have had a long-time relationship with a now-retired provider. We have been seeing each other once or twice a week pretty steadily for about twenty years. She is a wild-ass girl, but she rarely orgasms from anything other than DATY. Often it takes 20-30 minutes of steady licking to get her off; but she literally explodes, so it's well worth the effort. (I must confess, I just LIKE licking pussy, anyway!). Since we've been doing this a long time, I've gotten fairly adept a reading her signals (i.e., breathing, muscle tension, sounds, etc.) I have noticed that she sometimes gets a bit irritated with me and tells me to be "softer" or "gentler", but when I back off, she gets more uncomfortable and impatient. However, if I respond by pressing HARDER, she responds favorably. Likewise, when she tells me to go faster, I know that if I slow down to long, slow, full-tongue-length licks, she'll cum like a champ in no time. In short, she doesn't really know what she wants. I've observed the same behavior in other girls, just not over such a long period of time. Interestingly, I have watched her eat pussy many times, and she's very aggressive and will just devour a pussy. It's quite something.
Good eating!