Look past the headline figures, because management commentary will be key to Costco's success in the upcoming year.For most investors, earnings season is the pinnacle of each quarter. This is the six-week period where most S&P 500 companies lift their proverbial hoods and give investors an up-close look at their operating performance. There's arguably no better way to gauge the health of American businesses and the stock market than from the operating results of its most-influential businesses.But not every ...