Experiment with your grip; if you have big enough hands, you can get a nice twister by gripping it as DB suggested, but trap the seam on the middle-finger side of your index (you didn't mention if you are right or left handed, but that shouldn't matter) and try to develop a feel for the way the seam feels as it rolls off/over your index upon release.
Doing this should give you some movement, but you'll have to rely on your catcher to tell you how it's developing (how much break); don't get frustrated, because it takes time to attain consistancy.
You should also develop a 12-6 o'clock curve for "special" occasions; just try to make a mental note to let the ball roll over the thumb-side tip of your index finger as you deliver it.
An additional bit of work for the 12-6 is making sure you've propelled the ball to the plate before it breaks; again, it's down to practice-a few calouses should develop with sufficient practice.
You can, with work, develop a fade by rolling it off the other side of your index, so you can have fun with right- and left-handed hitters.
Hide/find your grip with the ball IN the glove before your stretch/delivery, and do every little thing you can to keep your delivery spacially consistent, relative to body-motion, arm-speed, and release-point;