My father worked with an Italian man whose father had handed down the perfect salad dressing recipe to him (father to son kind of thing for generations) As I recall, the recipe goes as follows:

A generous man puts in the oil;
A stingy man puts in the vinegar;
And a careful man puts in the salt.

Of course, an Italian would use wine vinegar rather than waste balsamic vinegar. I use this simple recipe with great success, adding lemon juice in place of some or all of the vinegar, ground pepper, a little thyme, tarragon, ground brown mustard seeds and/or garlic, depending on my whim.

1 clove garlic, minced
2 Tbsp raspberry vinegar
4 Tbsp mayonnaise
¼ tsp Dijon mustard

Whisk ingredients together well. Refrigerate til ready to use.