Mix sugar, salt, and tajin in a small bowl. Transfer to a small plate
Choose a small plate that fits the rim of your glass easily… pour the tajin mixture into the small plate and spread the mixture around the entire plate with an emphasis on the edges of the plate.
Coat rim of your margarita glass with lime juice by using a brush or placing the lime juice in a small plate, and dipping the rim of the glass into the lime juice.
Next dip the the margarita glass into the Tajin mixture.