There's no substitute for going over the bars a few times, helps you to plan a successful landing during those milliseconds you have as your rear wheel leaves the ground and your face starts moving toward the pavement.

I also think it helps to practice it in your mind a few times how you're gonna tuck in your chin and go into a shoulder roll, and how you are absolutely NOT gonna try to fight it by throwing out your arms and sliding on your face. Or you can just strap on a helmet and not worry about any of this stuff (bad idea).