Here are some basic symptoms of suspension damping problems that you might find affecting your bike. Remember these are only extreme examples - your symptoms may be more subtle. You may have to find an acceptable compromise on either end of the adjustment spectrum. It all depends on how the bike's handling feels to you. Front end dive while on the brakes becomes excessive.
Front end has a mushy and semi-vague feeling, similar to lack of rebound damping.
Overly harsh ride, especially right at the point when bumps and ripples are contacted by the front wheel. Bumps and ripples are felt directly - the initial hit is routed through the chassis instantly, with big bumps bouncing the tire off the pavement. The bike's ride height is affected negatively - the front end winds up riding too high in the corners. Brake dive is reduced drastically, though the chassis is upset significantly by bumps encountered during braking. The fork offers a supremely plush ride, especially when riding straight up.