Stay on the Trail
The “single” in singletrack means there should be just one path. Inching off the trail or going around something spoils the experience and turns the trail into a doubletrack and, eventually, a road. That also means that if the trail is muddy or filled with puddles, either ride straight down the middle and get wet or stay off the trail entirely. There’s nothing worse than a braided mess of trails because people didn’t let the dirt dry out and then decided to ride around the water.
In short, use some common sense out there. Be a good sport, don’t act like you’re more important than anyone else (you’re not), preserve the land, and have a good attitude. It’s pretty simple.