Since I can't find the place where I got my info (its at home) I will give you a quick run down of the basics.
There are several adjustments on the YFZ shock:
1) the threaded Preload adjustment. (the big nut thingy holding the spring) variable adjustment
2) Low speed compression adjustment. (the small brass screw on the reservoir) about 20-21 clicks BE CAREFUL ITS SEMI FRAGILE start about halfway,and adjust 2 clicks at a time until right.
3) High speed compression adjustment (the nut on the outside of the low speed adjustment about 3 clicks of adjustment only. Start with middle adjustment
4) Rebound adjustment (at the bottom of the shock) Generally set this slower so it does not rebound to quickly, and hit your butt causing ejection.
Like I stated before set these settings about mid way,and adjust from there to get the "just right" feel. When i find the post I used I will put it here for reference.