Served at our wedding, here is the recipe we used.
1 bottle reposado tequila (we use El Jimador)
1 1/4 cups fresh squeezed lime juice
7/8 cup fresh squeezed lemon juice
1 cup organic sugar
kosher salt (optional), for salting the rims
Make your simple syrup: in advance, heat the sugar with 1 cup of water in a small saucepan, stirring occasionally, until the sugar dissolves. Measure out 7/8 cup syrup and transfer to a quart-size container. Place in the fridge to cool.
Cut and juice as many limes and lemons as you need to make the lemon and lime juice. Important: do not use store-bought lime or lemon juice; only use fresh-squeezed.
Once the simple syrup has cooled, stir in the lemon juice, lime juice, and 1/4 cup water to create the sour mix.
Make each margarita: for one drink, pour 2 ounces of tequila and 2 ounces of sour mix into a shaker filled with ice. Vigorously shake the mixture so the ice breaks up a bit. Strain the drink into an ice-filled rocks glass and garnish with a slice of lime. Salted rim is optional. Repeat and scale this recipe as necessary – at our wedding, we used five liters of tequila, to make three gallons of margaritas!