The snatch and the clean & jerk are obviously high skill movements that require lots of practice, skill and focus. This focus, however, needs to be a narrow focus. Despite the skill required for these lifts, you'd be surprised how well the body can move correctly when the mind is focused on just one or two things.
For instance, going into a workout with the intention of just "staying over the bar," "finishing hard" or "driving the legs," will give you a clear focus on what to concentrate on for the day. A couple other things here and there might be off that day, but chances are you performed better on what you were specifically focused on.
If you're training on your own, and you don't know what you should simplify your focus to, seek out a coach with a good eye, so they can provide that focus.
This leads me to my next point - coaches sometimes need to simplify their focus as well. Trying to change or correct every little thing at once can do more harm than good. You start creating too many things for your athlete to think about. Give your athletes a limited and simple focus. Less can definitely be more. If you know there is one BIG weakness that your athlete has, work on just that one thing for a few sets, the day or week. From there, you can move onto the next big issue.