1. The best way to learn a raley is off the wakeskate. Since the board is not attached, the falls are a lot more forgiving. Also, getting some repetition on the trampoline will help you build strength pulling your legs back underneath you.
2. Too much speed into the wake prevents you from going up. You need the height so you have time to let the trick out and, most important, pull it in. Take a big approach, but just edge smoothly so you get more height than distance.