Boil whole, unpeeled potatoes in salted water, 3 qts water-2tsps salt.Boil until tender. A cake tester works great to check for doneness, it should easily go through potato.
Drain potatoes and set aside to cool.
Chop celery and onion.
Add mayonnaise, salt, pepper, vinegar, and sugar.
Stir to combine. Check seasonings and adjust to taste.
Refrigerate for 1 hour before serving, can be made a day ahead.
Notes
Try stirring a bit of bacon fat (2-3 teaspoons) into the mayonnaise before adding to potatoes. Quite tasty!