There are many, many, many (did we say “many”?) resources on the subjects of creativity and imaginative thinking. Following is a sampling to get you started. Whatever your preferred or natural approach to problem solving is, exposure to other methods and schools of thought on how to pursue solutions can help you expand your horizons and discover new problem-solving skills within yourself.
Michele Root-Bernstein recommends a classic, a practical guide for all, and a fictional exploration of creative imagination: