I just finished my first league this spring and I bowl in a small town 8-lane house which is notoriously hard to score in around the county. My avg. after the first 7 weeks was 147 but I finished the league with a 173 avg. (earning my league's most improved bowler award)
I'd say if you're using an old ball, you might try looking into a new, mid-priced ball that suits your style. I went from an old columbia ball (which got chipped around the holes) to a brand new Hammer Sling Blade in the middle of the season. That certainly helped since I've always gone down and in and the Hammer lets me do that better than before since it's RG is much higher than my old ball.
Another tip, is to find some bowlers who have success where you bowl. You can ask them about foot movement, shot tendencies, ball speed, or whatever. Through subbing for another league at my lanes, I've become friends with a guy who has been bowling for probably twenty years and averages over 200 in that house. We always talk about missed spares, how the lanes are reacting on certain nights, and new bowling balls that are coming out. Awareness and knowledge really help in bowling and having some does make a big difference.
