A lot of players question what they should be doing over the off-season... The off-season is really not an off-season at all! This is the time to focus on the three major categories of your game.
The three major aspects are...
Baseball skill set - This means its time to work on your baseball skills... Fix problematic mechanical flaws with your throwing, fielding, hitting, and pitching mechanics. Get this squared away now and ingrained in your muscle memory.
Strength - This is your time to get bigger and stronger. It is not always easy to get all your workouts in during the season... If you have not started getting in the weight room this off-season you are behind the eight ball! If you don't have a strength training routine, its a good idea to get with a strength training professional to help you with this. This is just as important as working on your baseball skill set!!
How you move - Moving in, out, and side to side is a huge part of the game. Quicker feet and a faster first step can help you get to more balls, and steal more bases! Work on your overall foot speed as well as your agility, and you will find yourself making more plays in the field and getting to more baseballs!