1. Rub a wedge of lime around the rim of the glass and then dip the outside of the rim of the glass in kosher salt.
2. Fill a cocktail shaker with ice.
3. Add the tequila, Cointreau and lime juice to the shaker and shake hard for about 20 to 30 seconds.
4. Strain the cocktail into the salt-rimmed glass (with or without ice) and enjoy!