My bike came with the manual for the Rock Shox fork, your LBS may have extras. Also the fork and shock were set by the shop during my fitting. We tested sag and my shop showed me all the settings. Rock Shox have a negative and positive pressure chamber, the negative is what you can adjust on the bottom. Even with a tutorial I still don't know exactly what to do with all the adjustments.
The dial is the amount of rebound or how much it compresses. You may have a little lock icon, that is locked out which will make it feel close to no shock at all. There are various placed in between. I like mine wide open (most rebound), my husband likes his in the middle. Some of the pressure settings are personal preference.
And yes sometimes this changes based on the terrain. My husband will go wide open on a rocky course. There is one race that has a road portion, we'll reach down to lock it out completely on the road.
Amanda
2011 Specialized Epic Comp 29er | Specialized Phenom | "Marie Laveau"
2007 Cannondale Synapse Carbon Road | Selle Italia Lady Gel Flow | "Miranda"
You don't have to be great to get started, but you do have to get started to be great. -Lee J. Colan