Rim either a margarita glass or rocks glass with wedge of lemon or lime. Place salt onto plate and twist rim of glass to cover. To release any loose salt simply tap on the bottom of the glass while holding it upside down.
Using jigger measure and pour tequila, Cointreau and sugar syrup into glass part of Boston shaker. Using lemon squeezer, squeeze lemon and lime juice into shaker and fill with ice. Shake vigorously for about 30 seconds.
Using hawthorn strainer, strain liquid into glass from metal part of shaker. If using rocks glass fill ¾ of the glass with ice first. Don't let liquid fill the glass; you don't want the salt rim leaching into the drink.
Drink and enjoy.