if you are hooking a plastic ball, it happens for one (or all) of three reasons.
1) You are putting far too many revs on the ball, this is easily rectified by not cupping your wrist on delivery and not lifting the ball, so it doesn't rev
2) the Lanes you bowl on are bone dry, unfortunately not much can be done about that, increasing ball speed could probably help.
3) your ball is heavily side-weighted, now this is unlikely, as plastic balls tend now to have much of a weight block, however, they often can carry up to 3 oz of top weight, which if drilled incorrectly, could all end up on one side of the ball, causing it to hook.
I'd suggest getting a competant driller to check the weight and balance of the ball, just to make sure it's not drilled incorrectly.