I gues the first thing I would do is take a good hard look at myself and see what my strengths were as a pitcher. Is my velocity great? If so, I would keep the 4 seam fastball and through it for strikes. If you are throwing from the straight over hand slot you realize that this pitch is not going to have much movement unless you have been blessed with that.
If your velocity is not overpowering, I would only throw the 4 seam fastball as a "show it to em" pitch high out of the strike zone.
Now we are into the realm of 2 seam fastballs. By varying finger pressure, index finger to make it move in to a right handed batter (from a right handed pitcher), middle finger to make it sail away. I found this better with more of a stiff wrist cocked all the way back. You have to experiment a little.
Then you get into the realm of turning the ball over which will make the ball move more.
If you are throwing from 3/4's the split seam fastball is a good way to make the ball move. If found it bast to also give it a little screwgy action.
This will reduce the velocity of you fastball though.
Hope this helps a little let me know, Ian.