Here are a few general comments about damping from my Zero's owner's manual:
Compression Damping - Proper compression will
allow the tire to track the ground over consecutive
bumps. Compression that is set too slow will
pack-up (feel harsh over consecutive bumps)
while compression that is set too fast will cause
the fork to bottom out harshly. If the fork is
bottoming out, turn the adjuster one click at a
time until the bottom-out stops. Adjust each fork
leg evenly.
Rebound Damping - This determines how quickly the fork returns to its
extended position after being compressed.