I like this article from AAII and Luke Wiley (he has a very similar book)
"Inversion. Such a simple concept. If there is a problem to solve, consider all the solutions that won’t work. In so doing, the correct answer reveals itself. When I first came across the above quote from 19th century German mathematician Carl Gustov Jacob Jacobi, it resonated with me. This way of thinking in reverse seemed to speak to the way I made decisions. Want to lose weight? Think of all the behaviors that will lead to obesity and do the reverse. Want to be a better father? Think of the things that would turn one’s kids away and do the opposite. Jacobi’s maxim seemed most appropriate to my career in finance, particularly as it relates to investing’s golden rule:
Buy low, sell high."
http://www.aaii.com/journal/article/finding-bargains-among-stocks-with-falling-stock-prices