It's easy to get homeruns at the Metrodome (where the Twins play). Just have all of your hitters aim towards right field. T balls will barely clear the fence but because it is so huge, they cannot rob it. This strategy also works at Fenway Park.
It is recommended that you have your power hitters first and your weak batters last. When you use your power hitters, try to smash the ball, while your weak hitters are probably fast so do not try to smash it.
To get doubles consistently, work on your timing enough so that when you hit the ball it says "Perfect". Then, aim your towards the opposite field and hit the ball to have it one hop the wall. The only players that won't make it are the ones with one star for their speed. If you have someone fast (for example, Grady Sizemore), you can even get a triple.