There are many spare shooting systems, some are good and some are outdated. I encourage my students to have a spare ball that does not hook so that they can line up the same way each time for converting spares. Nearly all spares except for double wood leaves should be shot with a spare ball. I would consider working with a qualified coach to become a good spare shooter.
You need to find a fixed target on the lanes to roll the ball over and adjust your feet accordingly. An example would be shooting all spares to the right of the headpin if you are right-handed over the middle (4th) arrow. A ten pin leave one might stand on board 36. A 6 pin leave might be board 33, etc. Just find your comfort zone and practice, practice, practice. You need to get comfortable with your spare ball. If you can throw the ball straight, you can be a very good spare shooter.
T. Scott
USBC Bronze Coach