Think of it as crossing over the idea-invention boundary, if you like. Start with a general idea and then build upon that idea by layering specifics and nuances as you move from idea to invention. Eventually you will have more than a mere idea and enough tangible and concrete that it will be worthwhile to inquire about obtaining a patent, perhaps by beginning the process with a patent search.
Inventors that want to be successful need to pursue inventing with a level of seriousness that goes beyond just tinkering in the garage. Sure, like every idea starting with an invention every invention starting with some tinkering and toiling is a given. But if you are not going to keep track of your efforts it will be extremely difficult to know what you did that worked, and just as importantly what you did that did not work.
Once upon a time, inventors needed to keep a good invention notebook in order to demonstrate the date they conceived of an invention, or aspects of an invention. This was necessary when the United States patent laws were first to invent. Since March 16, 2013, however, U.S. patent laws have become first inventor to file, so there really is a race to the Patent Office.