The adjustments do actually make a good bit of difference. The front ones are real easy to adjust. First sit the front end up on something so the weight is off the tires, i found that an old computer tower usually works nicely. Then just clamp onto the adjusting ring and turn it with some chanel lock pliers.
The rear shock can be tedious to adjust. It's best to remove the rear plastics and airbox so you have better access to the shock. Then you have to first loosen up the locking ring and spin it out of the way, and then turn the adjusting ring until you have the preload where you want it. The rings are usually a bitch to turn. The best luck i've had so far is this: First clean the threads real good with a brush and soapy water, then rinse and dry it off, and soak it with wd-40 or something similar. Then use a long flat screwdriver and a hammer to break the ring loose and turn it. You probably won't be able to turn them by hand even once you initially get them broke loose.