1. Add the tequila, lime juice, and triple sec (if using) into a cocktail shaker with some ice. You can also mix them by hand in a large measuring cup or pitcher.
2. Put some salt on a plate and rub the rim in the salt so it clings.
3. Shake or stir the margarita ingredients vigorously so they get well-chilled, then divide the mixture into the salt-rimmed glasses.
Serve over ice, if desired, or up.