Quickly press R when one of your players crosses home and the run will still count but in the following AB the runner will be back on 3rd base. Don't try this trick when the basses are loaded as your game will freeze.
First make sure that you are home. Next get into the bottom of the ninth with a tie. Then get your second baseman to replace the pitcher (that has been pitching for the entire game) have the second baseman up next. The guy that is up now needs to get a homerun. And the second baseman will get the save. You will see this after you quit the game!