When the U.S. stock market bottomed in the fourth quarter of 1974, the country and the economy were in an utterly sour state. For stock investors today, that piece of market history serves up a timeless lesson: Don’t wait for the economy to pick up and then speed up before you decide to deploy your own cash and make new buys. The market leads the economy. So keep an open mind and accept a strong follow-through as your timing signal.