I have heard a variety of ways to start off One Ball One Pocket. They all have the same general idea in common -- that being that you set up the shot such that the 'breaking' player has to open with a safety.
Weenie Beenie used to set up the ball very near the jaws of the opponent's pocket, so the 'breaking' player had to start with a take out (a relatively easy one). Sonny Springer also used that set up.
The one I like is with the object ball on the middle of the foot rail, and you have to 'break' from the same side of thable as your pocket (so you can't cut the ball in). I've also heard of starting the same way, but requiring the 'breaker' to drive the ball to one of the other three rails on their 'break' -- so they can bank at their pocket, but not shoot straight in. That sounds like a good way, too.