Add ice to the cocktail shaker. Then add the juice of 1 lime and tequila. Then add the juice of around 2 slices of orange and 1 grapefruit (equalling 1 oz, see my tip about freezing the orange/grape juice mixture). Finally add agave to taste (around 1 tsp) and a splash of water.
Once all the ingredients are in the shaker, shake it up. Use one of the squeezed limes to coat the rim of a cocktail glass, then dip in the margarita salt. Pour the completed margarita into the glass and enjoy!