A line cook in Seattle asked me why I was saving the fish bones

We were breaking down a whole salmon at the end of service last Tuesday, and I was putting all the bones and heads into a bag in the freezer. This new guy, Jake, asked what I was doing. I told him I was saving them for stock. He said his old place just threw them out. So I showed him how I roast them first, then simmer with some leek tops and fennel for a simple broth. It's free flavor, and now he does it too. What's something simple you do that new cooks are often surprised by?