Make limeade. Combine the lime juice, sugar and 1 cup water in a glass or plastic pitcher. Cover and refrigerate if not using right away (but no longer than 24 hours).
Finish and serve margaritas. Add the tequila and orange liqueur to the pitcher of limeade. Rub the rims of 6 martini glasses with a lime wedge, then dip them in a dish of coarse salt. In a large shaker, combine the half of the margarita mixture with half of the ice and shake 10 to 15 seconds, then strain into the prepared glasses. Repeat with the rest of the mixture.