Fill a cocktail shaker (or a mason jar with a tight-fitting lid) with ice, about halfway full. This will chill the drink and help blend the flavors.

Pour in 3 oz of tequila, ½ oz of orange liqueur, the juice from half a lime, and ¾ cup of watermelon juice. If using fresh watermelon, blend and strain it beforehand for best results.

Secure the lid and shake vigorously for about 30 seconds. You want the drink to be well chilled and slightly frothy.

Strain the margarita into a glass filled with fresh ice. Serve immediately and enjoy while cold.