Very simple to get this ending. Follow the game through and don't inspect anything you don't have to except to tie the door to the bar and the fork in granny's room, then once you reach the part with Mrs. Baker, sneak past her to the door and she will give you the car key. Make it past Jack then to the Garage, hop in the car and you will get the bad ending.
Here is a guide incase you are having trouble.
Here is a link to my guide on the True Ending: