Fruitful according to me is "good" and not necessarily optimal, combination of QUALITY and QUANTITY. We say a meeting was fruitful if a "lot of" issues were taken up and quite "many" of them got significantly, if not completely, resolved. Innovation similarly is the fruit of "fruitful" thinking. Innovative solutions are not always the best but are definitely different from most. What makes a particular thought process fruitful? Again it is the blend of quality "and" quantity of thoughts. Can adherently following one line of thought generate an innovative solution, well sure, if we are lucky enough! But not always. But if you have "many" such lines and you let them interact with one another, probability of finding something different would be reasonably high. Significance of quality of these thoughts is, of course, apparent.
It is often said that innovation comes from thinking OUT OF THE BOX. Well it certainly sounds cool but is also inherently flawed or incomplete. Because the so call BOX itself is guided and hence restricted by the perception of the person who is asked to think out of it. A person cannot possibly perceive of something, that is out of his perception. Therefore I guess the phrase should be reformed as thinking out of OTHERS' BOXES. Now that sounds doable, all we need to do is create a bigger box of INTER CONNECTED NEURAL PATTERNS. So that any stimulus can lighten up a comparatively larger portion of mind and create something which might not have been conceived otherwise. To build patterns we essentially need some raw material, reading "Varied" Texts is, I guess the best ingredient for making these mental patterns. Contemplation on things read, is the process that erects these pattern. Reading, therefore, gives you all that you need to construct these "interconnected" patterns and "thinking" actually gives them shape. To quote the Apple guy (Steve Jobs) "It was the calligraphy classes that I took after I opted out of graduation, that gave birth of artistically formed San Serif characters." Thus you never know when these dots get connected, but when they do..boy!! something new is bound to happen. New cause is very likely to produce new effect. It is the interplay of these fruitful patterns that we call lateral thinking, which often results in innovation.