Control homerun replay: After hitting a homerun, a replay of it will be displayed. When you see your batter heading home from third base, press various buttons to see different angles.
Better hitting: Immediately after the pitcher releases the ball, press Start. You will see where the ball is going and if it will be a strike or ball. Resume the game and move your batting cursor over it to get a nice powerful swing. This will help you improve your hitting. Note: You do not need to press Start directly after he lets go of the ball -- it just gives you more time to move your cursor after the game is resumed.
Use the pause technique before batting. When you see where the ball is going, try your best to get the ball as close to the point of the contact triangle (the part closest to the batter, not the thick part of the triangle). You will usually get homeruns or at least doubles.
Wait until the pitcher's arm is in motion and is coming forward, then swing. If it looks like a bad pitch do not swing. This strategy woks most of the time, and works well with players such as Giambi, Bonds, or A-Rod.