This post is being avoided like the plague. I'm kind of surprised.
Here's the primer on big spray
Step 1: Go fast
Step 2: Turn hard
Step 3: Hang on
Doing that really isn't conducive to running buoys, so I'll tell you this; as you ski faster and ski shorter lines, you will displace more water. Keep getting better at slalom at the spray will take care of itself.
if it is spray you are after, just lean back hard on the turn. Again, not the form you want in the course, but you'll get a bigger spray at the beginning level this way.
HO 410 and tjo gave you a good basis... the real thing they're getting at is that your spray will get better as your technique improves. You could make the biggest spray ever but your friends won't care as much if they have to pick you up after every turn. More hard work on your skiing and the spray will be there behind you.