Don't do it unless you have to. I'd rather not have more people risking their lives unnecessarily. Especially when "young" usually means "child or teenager", as far as I've seen.
If you must, make sure to train regularly. Keep a clear head, meditate. Don't allow fear or panic to control you. In time-sensitive situations, you will need your logical reasoning. Keep your body in shape. Stretch regularly, you don't want to pull a muscle during a chase. Don't trust the cops until they prove themselves.
Don't kill unless it's unavoidable, and make sure it is. Everyone can change if they try, you have to give them that chance. And don't just beat up the villains, look for the ground-level issues. Help the homeless. Find lost pets. Cover someone's groceries. Support local charities and shelters. It's more rewarding than capturing anyone, and it will help prevent future crimes from occurring.
I will be a hypocrite for this, because I want the next generation of heroes to have better habits than I do. Eat healthy, drink enough water, and get enough sleep. Especially that last one. Regardless of my own adherence to it, it will allow you to do better work, think clearer, and make better decisions. It may be the difference between life and death one day. If you're going to save anyone, you need to be healthy enough to do it.