Yesterday I was riding home from work on my regular commuter, and I thought about how I probably wouldn't still have this bike if it weren't for some sage advice that I received from the late Sheldon Brown. I had posted on here last September shortly after joining the site and becoming more serious about cycling, and I wasn't sure what to do with a broken bike. Here is the thread:
http://bikeforums.net/showthread.php?t=343096
Sheldon was the first to reply, and right away convinced me that the bike was worth getting fixed. I did and that bike once again became my regular commuter and I have put hundreds of miles on it since.
What have you learned from Sheldon, either through this site, his site, or from an email from him? I think this is the best way to remember a great man, by remembering his knowledge he was so generous to pass out. So what's your favorite Sheldon Advice?