Wet the rim of your glass (a lime works well for this) and add sugar to the rim.
Shake the tequila, orange juice, and lime juice together in a shaker and pour into prepared glass.
Garnish with a lime wedge.
If you don't have a shaker, you can just stir your drink in the glass.
Also, many people prefer to add 1-2 teaspoons of sugar to this drink for added sweetness.