For many years my husband and I have marveled at friends who seemed to serve their guests effortlessly. Short of hiring a caterer, we’ve concluded the key is to be prepared. Here are three lessons we’ve learned-the hard way—through some embarrassing failures. Lesson #1: Never prepare a first-time recipe for guests; #2: Do as much as you can the day before, or at least hours before guests arrive; #3: Know your limits. If the recipe sounds too complicated, it probably is.