It has been said by so many coaches that it feels like a cliche to repeat it....but it's true.....DO NOT LABEL YOURSELF A GUARD, FORWARD OR CENTER......just become a player.

By that I mean you need to learn the fundamentals of an all round player, not just of a position.  First of all, you have no idea what postion you'll be playing in 5 years from now.  Second of all, no coach wants a big man who can't dribble or a guard who can never post up. 

You need to learn the skills and understand the roles of all 5 positions on the court.  If you spend the majority of your time working on your ball handling, shooting and passing, you will be ready to play any position needed when it comes time for you to pick your position.

P.S.  The best example of someone who didn't let traditional wisdom of "put the big guys inside with their backs to the basket" is Kevin Durant.  No doubt he would have been a solid NBA player as a back to the basket big man. However, but by working on his spit second "guard" skills at a young age inspite of his height, Durant has become arguably the best in the world.