Get a cocktail shaker and fill it halfway with ice. If you are going to salt the rims do so now – wet your finger with simple syrup and rub around the rims of the glasses. Sprinkle salt in a dish or use a pre-made mixture and dip the rims of the glasses in the salt.
Cap the shaker and shake vigorously. Add fresh ice to the glassware and pour the margarita between the two glasses. Don't pour the liquid over the salt as you don't want a salty drink.