Cutting Fabric/Trimming Edges of Fabric and Selvedge for Sewing?

I'm prepping a few yards of fabric for my first pattern-based sewing project. In my instructional book, it says that I should first wash the fabric (a cotton shirting fabric) and to do so, I should trim the raw edges with pinking shears so that they don't unravel. Does this include the selvedge?? Because 1/5th inch of the selvedge looks a bit frayed. And if I have to trim the selvedge, how will I know after washing which side is the selvedge (so that I can cut the length along the selvedge) and which is not?