Expose yourself to diverse stimuli, and know when to stop and walk on the beach, etc. Don't get so far into the problem that you can't get out of it. Let your intuition work with you. Be eclectic and focused in your work. Invention is discovery.
Discovery is connection, extension, bridging.
Learn many techniques. Fit them to the problem. Keep your suitcase full of tools. Use them appropriately. Learn to use all parts of your brain, separately and as a whole.