To make old-fashioned potato salad, cut cooked, cooled potatoes into cubes, and whisk 3 tablespoons apple cider vinegar and 1 teaspoon salt together. Mix the potatoes with the vinegar, and add 1 cup mayonnaise, 3/4 cup chopped celery, 1/2 cup chopped onion and 3 chopped hard-boiled eggs to the salad.
To make potato salad that includes mustard, combine 4 cups of cooked, cubed potatoes, 3 chopped, hard-boiled eggs, 2 thinly sliced celery ribs and 1/4 cup chopped green onions. In a separate bowl, combine 1/2 cup each sour cream and mayonnaise, 2 tablespoons each vinegar and sugar, 1 teaspoon prepared yellow mustard, 1/2 teaspoon salt and 1/4 teaspoon pepper. Pour the mixture over the potatoes, and chill the potato salad for at least one hour before serving.
To make potato salad with red potatoes, boil 3 pounds of unpeeled red potatoes until the potatoes are tender. Allow the potatoes to cool slightly before cutting into 1/2-inch cubes. Pour 3 tablespoons of white wine vinegar evenly over the potatoes, and combine 1 cup of mayonnaise and 2 tablespoons of whole grain mustard in a separate bowl. Add 4 chopped celery ribs, 4 sliced green onions, 2 tablespoons flat-leaf parsley and the potatoes to the mayonnaise mixture, and stir gently to coat the potatoes in the mixture. Add salt and pepper to taste, and refrigerate the potato salad for two hours before serving.