I keep my selvedges on until I cut the fabric even when it doesn't have any information as often happens with fat quarters. It lets me know which way is the direction of grain. It was beat into my head as a youngster to pay attention to the grain. It also lets me know whether or not I have full width of fabric, or if I've already cut along the long edge.
Sometimes I will write a message on the selvedge, like I have a piece of "scrub" fabric I like to use in my alphabet quilts because it has X-Ray on it, I wrote the poly content percentage on the selvedge. Other times I might date it, or other comments.
I'm a big believer in prewashing fabric, all you have to have is one project ruined to become a true believer! I mostly work with scrap/charm quilts and so it is important to me that the fabric is ready to go. LOL happens I have some fabric in the washer/dryer right now. In the picture below is the fabric that ruined a quilt I made, I had prewashed the fabric once and then didn't bother my mind about it because I'd never had a problem. Forget the maker but it was reputable, I used swirly print in blue with no problems. The maroon leaf fabric bled so much that it turned all the white fabric into baby pink -- not the sophisticated grey/silver, blue and maroon I had designed.
I found the swirl version (now orange) at a Goodwill. So far I've washed it 7 times and it still runs like an Olympian. Hard to believe they started out as the same color.