Salt the rim (optional). Run a lime wedge (the juicy part) around the top rim of your serving glass. Fill a shallow bowl or plate with salt, then dip the rim until it is covered with your desired amount of salt. Set aside.
Make the margarita mix. Add tequila, orange liqueur, lime juice and a few ice cubes to a cocktail shaker. Shake or stir for about 10 seconds, until combined. Give the mix a taste and if you would like it to be sweeter, stir in your desired amount of agave or simple syrup to taste.
Serve. Fill serving glass with ice and pour in the margarita mix. Garnish with a lime slice, serve and enjoy! Cheers!