In How to Break 90 , two PGA teaching pros offer a sensible approach to shooting sub-90 scores by eliminating the most dreaded numbers on a scorecard--double, triple, and quadruple bogeys. They focus on simple strategies, such as playing toward a personal par of "level fives" and how to finish the job on the green.
Before reading this book I broke 90 about half the time. This book has helped me break 90 more often. Course management and playing for bogeys has resulted in more pars and fewer doubles and triples. I practiced and adopted the authors' techniques for pitching and sand shots and am very happy with the results. I've played about 6 times since reading and practicing and shot over 90 twice and 84 once - good results for me. Of course it might just be all the practicing, but I know the pitching technique has saved many strokes.