Here are some bits of advice that I have received in my coaching career that I found especially helpful:
Be yourself – Define yourself and be the best you, you can be. No one can fault you for this.
Coach the person, not the shot putter, basketball player of swimmer.
Know the basics. Master the basics. Never deviate from the basics.
Make the champions choice. Invest in the process, no shortcuts. Being comfortable with being uncomfortable is the champions way.
These recommendations are very straight forward, nothing complicated and very basic. They have served me well for 51 years.