Store dressing in the refrigerator for up to a week.
Authentic extra virgin olive oil will harden in the refrigerator. Transfer the jar to room temperature about 20 minutes before serving so the olive oil can melt. Shake vigorously before serving to re-emulsify the ingredients.
The traditional vinaigrette ratio is 3 parts oil to 1 part vinegar. I like mine less oily and more tangy, so I use more vinegar. If you prefer closer to a 3:1 ratio, use 1 cup olive oil and 1/3 cup vinegar.