I got this recipe from my mother and has been in my family for generations. It's very simple and delicious and what you will find on most French dinner tables.
1 cup wine vinegar
2 cups oil
about 4 tablespoons Dijon (Grey Poupon) mustard (it helps to bind the oil and vinegar together and give it some flavor)
Blend all in a blender and store in glass jar in refrigerator. You can add salt (if you want) and grind a little black pepper over salad to taste. Shake the bottle before putting on salad.