Boil macaroni in salted water until tender
Drain and rinse with cold water
Let the macaroni cool completely
Chop celery, onion, and any other desired vegetables
Add mayonnaise, mustard, salt, and pepper to a large bowl
Mix in vinegar or pickle relish if desired
Add the cooled macaroni to the bowl
Stir in the chopped vegetables
Add boiled eggs, ham, or tuna if desired
Mix until everything is evenly coated
Chill in the refrigerator before serving
Taste and adjust seasoning before serving