When training for baseball there are a few key things you will want to concentrate on, namely focus, hand-eye coordination, running abilities and stretching.
The reason focus is important in the sport of baseball is because when you are out playing a game if you are easily distracted you are likely not going to play your best and will have a hard time hitting the ball.
In order to improve this you should practice in areas that do have distractions so you can simulate and actual game environment. Since you never have control over what the crowd does you need to learn how to maximize what you do have control over - your focus and skill level.
Next, when training for baseball you need to have good hand-eye coordination. If you lack this you will likely be striking out quite frequently. The best way to improve this trait is to simply practice sport-specifically. In order to get better at hitting the ball, practice hitting the ball. The more you work at it the better your judgement will become and the more in tune you will be with your body and the movements it makes.
Running is also going to be very important for this sport as you will need to be fast and have a good reaction time. If you are not able to sprint from base to base as quickly as possible you are not going to be successful as a player. To improve upon this skill, practice by doing sprint training on a treadmill. Do intervals of about 30 seconds where you go as fast as you can, followed by a period of about one and a half minutes of rest. Repeat this process six to eight times then perform a cool-down.
Finally always make sure you take the time to stretch out your shoulders before and after a practice or a game. Due to the sheer, high speed swinging motion you are putting these joints through, if they are not loose and limber you could experience ligament or muscle tears.
A proper warm-up and stretching session is vital to staying injury free.