I found this wonderful tutorial online and thought i would share with everyone. If you've never checked your air brakes you really should. Once you figure out how to do it, it literally takes less than 1 minute per wheel to adjust and it could save your life and the live of others on the road. Ever see signs on top a mountain pass that reads "all trucks must check brakes" this doesn't mean that drivers should step on the brake pedal, it means they should stop their trucks, get out, and manually check to see that their brakes are in proper adjustment.
here is an excellent link that describes in detail how to adjust your brakes...using only a 9/16 wrench.