Your conditioning program must keep the dynamics of baseball in mind. You're not training for strength, but for strength over a range of motion with velocity.

Strength X Speed = Power!

• Full-range weight training (not for bulk, for power).
• Anaerobic training (for proper energy system use) 3 times a week.
• Aerobic training (for endurance, especially for pitching) twice a week.
• Train in sets and reps (to build intensity, measure improvement, spot weaknesses).
• Periodic training (over several weeks, to build intensity from pre- to post-season.
• Reduce injuries and improve stamina. It should be one of your main goals for a conditioning program - to enjoy season-long participation and performance.
  

Working with Weights:

• Be sport-specific: Baseball is a dynamic sport - always exercise muscles in the way you need to use them in practice and games - the proper arc, rotation, and extension (see Range of Motion).
• Maintain muscle balance: Major muscle groups need to be worked on both sides of a joint - i.e. work biceps AND triceps equally.
• Be systematic: Do weights in a program - max. three times a week, set workout length, a number of exercises, each done a fixed number of repetitions (see Reps and Sets).
• Build strength AND speed: Varying weights during exercise can improve overall power (see Pyramid System).
• Really work at it: For maximum training, muscles have to be challenged - weights (and/or velocities) have to be increased over time. (See Off-Season for details.)
• Rest builds muscles too: There's a difference between overload and overtraining. Give yourself a day off between weight sessions to let muscle tissue recover and respond. The next session will go even better.
• Don't start yet: Don't grab the weights still you're ready. Every weightroom session should start with a full-body warm-up and stretching routine.