I like to center the stacking ball between the points of the corner pocket, just so I can have a reproducible position for it. You can use a small washer to balance the balls if you don't have a stacking ball.

I like to freeze the cue ball to the short rail at the 1st diamond. Some players will attempt to freeze the cue ball to the stacking ball, or at least get it as close as possible. Both methods work. I use a 1/2 ball aim with 1 tip of running english. I usually make adjustments using my aim.