Fork designers keep us all on our toes by changing the locations of damping and preload-adjusters from year to year and model to model. Here’s a couple of examples, but refer to your owner’s manual to find which knob does what on your forks. Sometimes, generous designers label the knobs on the forks for you – this makes life a lot easier!
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES
See also bike maintenance tips, tricks and techniques “Front suspension”