"For investors, the energy business used to be a pretty simple play: Buy a stock and stick with it. Until a couple of years ago, soaring oil and natural-gas prices made any energy bet pay off. Not only did oil and gas stocks rise, but so did alternative-energy shares: With fossil fuels getting pricier, solar and wind power looked much more competitive. Then came the crash of 2008, and all that went out the window. These days, the energy sector is about as complicated as it gets, with a range of issues buffeting stock prices and making it tough to know where to put your money—and when to do it."