Interesting article in CACM, March 1999: Rickert and Nagy: "Focus Groups, Theory or the Kid in the Garage". They discuss the sources of invention. Some teaser quotes follow. Check it out!
"... the mind of the inventor is that of a curious child, not that of a smart adult."
"Richard Levy ... states that children invent because they don't realize that they can't."
"Mihaly Csikszentmihalyi stresses that inventive individuals must first master the 'symbolic systems' of their fields. The symbolic system may be grammar and style, mathematics, music theory, engineering fundamentals or theories of human-computer interaction. ... If one is to create a new way, he or she has to be familiar with the old way, or the dominant paradigm."
"... what seems to be imortant for invention is being 'less afraid of making mistakes than doing nothing important enough, difficult enough or worthwhile enough to cause mistakes.'"
"... invention and innovation proceed primarily by emulation of prior art."
"... the only contribution of scientific theory to the evolution of the steam engine was the notion of vacuum. The rest proceeded through many inspired iterations of trial and error."
"Pay attention to the things people use that can be made better, listen to and observe regular people, know your field, but most of all, occasionally stop acting your age and start acting like a kid."