One of the most important lessons I learned was to always pay attention. Time and time again, someone isn't paying attention and they knock over a tripod with a camera on it. It is then up to the reflexes of the person next to it to catch it so that the camera doesn't break. This has happened multiple times to the point where I think that my reflexes are honed past the point of a ninja. If no-one is around you when you bump into the camera, you may have just destroyed a thousand dollar camera.
A lesson that I learned which is paramount in value is to never be shy. In our class, we tend to ask a lot of strangers for things, whether it be monetary through donations, or a donation of their time for an interview. Being shy can make you lose a lot of opportunities. You have to be outgoing and not let a man on the street walk away from an interview just because you couldn't muster up the courage to ask him.
The third and maybe most important lesson of all the three is not to fool around. When you fool around, nothing good ever happens. You may knock over a tripod, you may trip over a wire, you may rip a mic cable. Only bad things happen when you fool around. Fooling around puts you, others around you, and the equipment you need in danger. Not fooling around is not hard and it is an excellent way of avoiding havoc.
In conclusion, the three most important things that I have learned in my three years of media are lessons that include being aware of your surroundings, being outgoing, and not playing around. Following these three lessons can make your, and the people around you's life a whole lot easier.