Add tequila, lime juice, Simple Syrup and orange liqueur. Cover and shake until mixed and chilled, about 30 seconds. (In general, the drink is ready by the time the shaker mists up.)
Place Lime-salt-sugar on a plate. Press the rim of a chilled rocks or wine glass into the mixture to rim the edge. Strain margarita into the glass.
Put the sugar and water in a small saucepan. Cook over low heat, stirring, until the sugar dissolves. (Alternatively, heat in the microwave.) Store in a sealed container in the refrigerator for up to 1 month.
Blend together lime, salt and sugar in a small blender or mini food chopper.
