Spread the salt on a small plate, moisten the rim of a 6-ounce glass with the lime wedge, and upend the glass onto the salt to crust the rim.
In the bottom of a cocktail shaker, muddle the sprigs of fresh herbs with a cocktail muddler or a wooden spoon until roughly mashed. Add the tequila, lime juice, orange liqueur, agave syrup and ice. Cover and shake vigorously until frothy and cold; tiny ice crystals will appear in the drink after about 15 seconds of shaking. Strain the contents of the shaker into the glass and serve immediately.