It really all depends on your riding style. XC'ers like minimal sag so their fork bobs less and they can transfer more power to the ground. I was going with 25% sag on my 5" dually for bumpin' around. I did a few jumps and kicked it all the way down to around 10% because I was bottoming out.

If you have an "bottom out" adjustment or high and low speed compression dial, you can run more sag and still not bottom out. I only have rebound, so I have to run more preload to keep it from grounding. If you want it super plush, go with 33% sag, little low speed compression, and either alot of high speed compression or more bottom-out pressure.

If you want more efficiency, go with 15% sag, lots of low speed compression or platform...which ever ya got, and then set your high speed compression based on your racecourse.

So, rule of thumb is to start out with around 15-25% and then go from there based on your riding style.