There's no magic button. If their game is smaller then they are using less art, smaller art, less sound, smaller sound etc. The trick is to learn how to optimize the use all the stuff that makes your game.
How big are the images you're using? How many frames are you using per animation? How much music or sound does your game include?
best of luck,
-Mike
I'm talking about Real Racing having less memory than a game I optimized and made sure all images and sounds were incredibly low in memory. I done a college course and this was pretty much the only thing I was good at, editing images and stuff. But I'm not sure if it's to do with the way things are exported.