"Shoot 'em in the middle"
Fine words from a Gentleman from Indiana!
I used to find, the key to practising for the plate match was to make everything varied. If I usually shot left to right, I'd spend time shooting them right to left.
I also used to mix up the directions depending on the distance I was shooting from, so 10&15 yards I'd go right-left, 20 yards (prone) I'd go left-right and 25 yards I'd do a string each way.
I shot prone from 15 yards back, so to avoid the tendency to get into a habit, I'd practice shooting standing all the way through. I've also shot the entire stage weak hand (supported) and standing all the way back.
Everything was really just to make sure I concentrated on the shot itself, rather than get into a set pattern or rhythm. Still never stops you from making stupid mistakes though!