Quoting Gary Valentine...
While its certainly possible to learn power versions first then squat lifts, Ive had better success teaching squat versions first. Under the eye of a qualified caoch each workout, the lifter will be instructed to pull properly, i.e, similarly to the squat versions. There should be no difference in the pull, whether power or squat style. In reality though, many beginners who train on their own resort to a back swing- heavy-single-thing which not only doesn't apply to squat lifts, but probably inhibits learning them when it becomes an ingrained motor pattern (I know this from experience!).
I teach the snatch balance sequence outlined in USAW Club caoch manual, but I go from the Drop Snatch to "Snatch from Full Extension, to Hang Snatch to Snatch from floor. I've had great success with it. I'm in no way saying its the only way, but it works.
Practice the Drop Snatch a lot. That's standing with empty bar, snatch grip, behind neck as if to squat. Put your feet in the pull position however. Just drop down into an overhead squat, picking feet up to move out to slightly wider squat stance. Here's the catch - when you get good at those, start with knees slightly bent, so the bar starts even lower. This is all for learning body speed, essential to lifting great weights, and I believe what sets OL apart form other barbell feats. There's something about throwing yourself under a limit weight thats a bit crazy and exciting!
Then go to snatch from full extension. I've posted on this before, so check through the notebook. You may need a lighter bar, or more emphasis on pulling body under bar. The bar is higher in full extension than in the bottom of an Overhead Squat, so its all a race. I simply ask my lifters to show me how fast they can get into the squat and start coming up before the bar starts coming down.