Cut a 1/4 wedge out of one of the limes. Run the lime along the rim of your glass.
Lay down some salt on a flat surface, then press the juiced rim of the glass into the salt until coated all the way around.
In a cocktail shaker (or a large mason jar) add the tequila, triple sec, lime juice, and simple syrup. Plop in a few ice cubes.
Seal and shake the cocktail in a circular motion (think bartender-style) for about 15 seconds.
Add fresh ice into your margarita glass.
Strain the margaritas into the glass. Do not add the shaken ice in it, use new fresh ice in the glass! This helps the margarita stay cold, and the ice won't melt quickly.
Cut a lime circle out of the other lime, then make a small sliver in the circle. Add the lime garnish to the rim of your glass. Sip and enjoy!