Dice beets and put into a saucepan with the beet liquid from the can. Add the vinegar and sugar. Cook for a few minutes. Cool mixture so beets will marinate in the sweet sour liquid. Then drain off liquid.
To the beets, add diced cooked carrots, chopped celery, onion, salt, and enough mayonnaise to mix together. (Half the mayonnaise and half the French dressing give a good blend for the mixture.) Serve on lettuce.