Adjusting the rear shock is as easy as 1, 2, 3.. But, like the front forks, changes should be made one at a time to gain an accurate understanding of how they affect the bike.
Once you are familiar with the settings on your suspension, you can quickly and easily adjust them to suit different terrain. For example, you may know the clicker positions for when you ride in the sand dunes. But when you are riding on your local motocross track you know to tune them to a different setting.
The high-speed compression relates to the 2nd half of the suspension stroke. The rest of the clickers only control the 1st half of the suspension stroke i.e. the low-speed compression.
Softening the HSC can help make the bike ride more smoothly over choppy land. Have a play with it and feel the difference for yourself.
Remember, having the clickers wound all the way to hard puts more pressure on the shock. Keep it a few clicks out.
Try screwing it in clockwise to allow the rear wheel to stay in contact with the ground over larger, rolling terrain.
If you screw it out anti-clockwise this should give you a better ride over rough bumps that are close together by allowing the shock to rebound faster and 'hug' the flow of the terrain.
Be aware you can actually cause the suspension to 'pack' by hardening (or slowing) the rebound too much. This is when the suspension doesn't have a chance to extend back properly before absorbing the next bump/s. It continues to compress before finally bucking back, causing one to think that the suspension doesn't have enough rebound dampening, when it actually has too much.