Depending on the damper you have, start with the manufacturer's manual. You may need some special tools and most can be found here for a reasonable price.

http://www.resuspension.com/Tools-p-1-c-7.html

http://www.resuspension.com/Technica...tion-sp-4.html (For Ohlins tool manual)

I partially disagree with GA. Yes you need access to a dyno to validate your valving (why I bought mine), but you can still revalve without one. You will need to work with the manufacturer on selecting valving. They will work with you on your particular setup to make a good valving selection (they'll run a test shock with the valving or have already done so). If you know what you want the curve to look like they can help you come up with a good valving to match. The best bang for the buck here is Bilstein and they are quite liberal with technical support. Old Carrera/QA1 GP series are good too, but parts are difficult to find.

Here are some links:

http://www.honda-tech.com/showthread.php?t=2415915 (DIY Bilstein rebuild instructions)

http://www.bilsteinus.com/race.php (Bilstein tech info)

http://farnorthracing.com/shocks_2.html (DIY Bilstein street shock to rebuildable race shock conversion with Fox canisters)

For direction on how to figure out what dyno curves you want/need start reading here:

http://farnorthracing.com/autocross_secrets6.html