Too many of us have greeted unexpected guests with a half-empty bag of pretzels and not much else. But this season, prove yourself the effortless host by trying this trick: As you grocery shop, think in combos. Certain summer ingredients are simply meant to go together — such as tomatoes, basil and mozzarella, or marshmallows, chocolate and graham crackers. Here are 10 more delectable combinations that instantly brighten a backyard barbecue (and will impress all your friends!).