What I used to do in practice was find a line, and get confortable on it, and shoot a few good games. Then even if that line is still holding well, change lines completly, so I was somewhat uncomfortable and try and produce some good scores.
Other then that, concentrate on your sparing. Perfect example of that... I was bowling league one night and the pattern they put down was REALLY TOUGH, and I didnt have much of a look in at all. I didnt open a frame in the 3 games, shot 620. Its a grind, but It was the most satisfied ive felt after league ever.
good luck and high scoring
matt