Charles Noble offers some excellent advice to young musicians. Much of his advice makes sense for not-so-young musicians as well. And some of it might even make sense to non-musicians.
One thing I would add is something that Charles demonstrates consistently. Being able to express yourself in writing is a very valuable skill for musicians to possess. It is sometimes hard won, but it is a skill worth developing.
It is very easy, in our current lax educational environment, for high school musicians to "get by" on their talent, and make it through high school without understanding the mechanics of grammar. It is very easy for non-musicians to do it as well. Many high school teachers don't realize (like my teachers didn't realize) that making a life in the musical world involves much more than playing well. The advice I would add to Charles' list would be to go out of your way to learn how sentences and paragraphs are put together. Demand as much from your English teachers (in college as well as in high school) as you demand from your music teachers, and repay them for fulfilling your demands by putting serious time into improving the mechanics of your writing.