from the MX-tech web site
Setting the rebound:
1.) Find a relatively fast trail with braking bumps, rocks and roots leading into the entrance of a corner. Reduce (Turn clicker out) the rebound damping until the rear end begins to hop or feel loose. Finally, increase (Turn clicker in) the rebound damping until the sensation goes away.
2.) Find a log or ledge that tends to bounce the motorcycle after hitting it. If the rear end bounces up uncontrollably, add rebound. (Turn clicker in)
3.) Find some large whoops. The motorcycle should track straight through the whoops with the rear wheel extending to the ground before the next impact. If it does not perform as described, as above, it is packing and the rebound dampening should be reduced! (Turn clicker out) (Please note the guide for sand set-up, as these rules don't apply for sand.)
4.) Find a corner with acceleration bumps, rocks, and roots on the exit. The rear of the motorcycle should follow the ground. If the rear end "breaks up", reduce the rebound. (Turn clicker out) (If this fails soften the compression two clicks.) (Turn clicker out)
There is lots more there, check it out.