Easy strikeouts:
Once you get two strikes on a batter, always throw a low inside curveball or slider. You will almost always get a strikeout.

Homerun hitter:
At the main menu, go to "Rosters" to create a player. Enter the player's name as Erik Kiss. He will hit a homerun every time the ball is hit.

Trades:
In season mode, the CPU will accept all your trades (at least in rookie mode). You can trade players that you do not use a lot for other players on other teams that are very good. For example it is possible to trade Marcus Thames to the Diamondbacks for Randy Johnson.

Perfect game:
Use Barry Zito or create a player that has a good slider and curveball. Throw the slider two times to the opposite side that the pitcher throws. For example, Zito is left-handed, so throw it to the right side (inside of a left-handed batter). This will cause the batter to think it is either to the inside or to the outside. The pitch must be at the edge of the strike zone. After that, throw a curveball in the upper inside or outside corner. He should strike out, pop out, or ground out.

Easy homeruns at Fenway:
If you have a big hitter such as Manny or Vlad, hold the Left Analog-stick diagonally towards the Green Monster. This will make almost every inside pitch or icon in the hot spot go over the wall for a homerun.