Mix sugar and salt together on a small plate. Run a lime wedge around the rim of your glass, then dip rim into sugar and salt mixture.
Place strawberries at the bottom of the glass and muddle until crushed, then fill the glass with ice.
Fill a cocktail shaker with ice and add in tequila. lime juice, orange juice, and agave nectar. Secure lid and shake for 30 seconds, then strain into glass. Gently stir to combine muddle strawberries and shaken margarita.