[jwalsh07]

If you score on the first 4 downs, you win.

[tennmountainman]

Or if the Defense had scored on a fumble or interception.

[Christian4Bush]

If you score on the first 4 downs, you win.

If you score a touchdown on the first possession, you win.
If you turn the ball over and the defense scores, they win.
If you score a FG on the first possession , the opponent gets a possession, to tie and continue, or to win.

Or something like that.