I took the recipe from Alice Waters, but it is made mostly by taste. The ratio of vinegar to oil is 1 to 3 or 4, depending on your preference. For a medium salad, pour a tablespoon of vinegar directly into your salad bowl. Whisk in a pinch of salt and taste for balance–it will be strong, but the salt should smooth it out a bit. Add 3 tablespoons of extra-virgin olive oil and a few grindings of pepper and whisk until emulsified. Taste and see if it needs more oil, which will soften it further. Place your salad in the bowl and toss.
Truc (Tip): Red or white wine vinegar is fine, but sherry is superb for its subtlety. You can also substitute fresh-squeezed citrus juice and zest.