Cut lemon in half lengthwise; cut one half into eight thin wedges. Thread olives and lemon wedges onto toothpicks for garnishes; set aside.Using the lemon half, moisten the rims of eight large cocktail glasses. Sprinkle salt on a plate; hold glasses upside down and dip rims into salt. Divide the salad greens, tomatoes, onion and sliced olives among prepared glasses. Top each with a prepared toothpick.