In the following video, Fool analyst Blake Bos takes a look at margin debt, or the degree of leveraging taking place in today's market. He discusses how the results he sees can often be an indicator of a hot market. He also highlights several stocks that have had remarkable run-ups recently and that he wouldn't recommend betting big on at the moment. Blake also shows investors that although you should never attempt to time the market by trying to predict crashes and selling beforehand, understanding this indicator of an overly hot market can be a great tool for knowing when to buy.