As Ironhorse said, make sure you are entering the season physically prepared, meaning you are in the batting cage and the weight room in Oct-Dec.
But, as Yogi Berra said, "baseball is 90% mental, the other half is physical". Don't neglect the mental aspect. Practice visualization before the season and use it as a tool throughout the season. I wrote an article on visualization on the Power Alley website, here is a portion of the article that may help:
"Visualization is using your mind to see yourself accomplishing a particular act before you set out to do it – hitting a solid line drive up the middle, making a diving stop on a grounder, or battling back from a 3-0 count to strike out the hitter. You SEE yourself accomplishing it in your mind, so you BELIEVE it can be done. To paraphrase Henry Ford, once you THINK you can – you’re right. You can do it!
Let me give an example of how to use visualization to prepare for a plate appearance. The key is to visualize EVERY DETAIL, incorporating all of your senses. Start by closing your eyes and taking a few deep breaths. Put yourself in the on-deck circle, preparing for your at bat. See yourself walking up to the plate. Feel the dirt underneath your cleats as you go through your routine of getting set in the box. Hear your batting gloves sticking to the grip on the bat. Look up and watch the pitcher get the sign from the catcher. Watch his wind up, and pick up the ball as he releases a fastball grooved right into your wheelhouse. Hear the spin on the ball as it approaches, and feel your body executing the mechanics of the perfect swing. See and hear the ball hit the sweet spot, and feel the sensation of the contact through your hands and up through your arms as you watch the ball shoot over the pitchers head and up the middle (or over the center field fence – it’s your visualization exercise)."
Good luck, and if you have any questions send me a note.