If you hit it over the fence on the leg side twice in one over, you get 6 runs and you're out. Batsman and bowler take turns getting the ball.
Hit it over the fence to the off side and you're out for no runs (it's much harder to get into the garden on the off side) and the batsman gets the ball.
Hit a window and you're out.
Hit it through an open window and you get 50 runs and are out.
Play the ball onto the fence behind you and you're out.