Find a team in your area or keep in contact with a team over email. The only way to learn from mistakes is either to make them yourself or have someone else make them for you. If you talk with a team, they can help you with all the really stupid mistakes (like forgetting to power on the robot before matches) and how they fixed them.
If you don't know a team, get
this book instead from our buddies at Pope John Robotics. Actually, get it regardless.