1/2 cup fresh-squeezed lime juice
1/2 cup tequila
1/2 cup Triple Sec
7 packets of Splenda or Truvia (or sugar equivalent)
Let me be adament here ... there is no adequate substitue for fresly squeezed lime juice. I've found that most bars and restaurants opt, instead, for pre-made mixes or frozen lime juice. Trust me, although it may take a little bit of elbow grease to squeeze these green gems, it's worth every bit of the effort.
The only reason I don't indluge in sugar is because I can save a few calories by using a substitute and, in my case, that's a good thing. If you prefer sugar or simple syrup, by all means use it. Truvia, a brand name for stevia, is a natural plant sweetener that I've become quite fond of. Made from the leaves of a tropical plant related to the sunflower, its taste has a slower onset and longer dureation than that of sugar. It's actually 300 times sweeter than sugar but has a negligible effect on blood glucose.
On the Rocks
Mix all the ingredients together in a quart-sized container with a tight-fitting lid. Add ice to the brim, cover and shake. If you like a salt-rimmed glass, rub a lime wedge around the edge of the glass and dip the rim in a saucer of margarita salt.. Fill the glass with ice and pour in the chilled concoction from the shaker.
I've had trouble getting a really good, icy margarita using a blender. Often, by the time, I manage to get it slushy enough, it's too watered down. The Margaritaville blender solves that problems by first shaving the ice then dispensing it into a blender where it's easily and quickly mixed with the lime juice and spirits liquid. If you're adverse to the idea of a machine dedicated to the task of making perfect margaritas, the Margaritaville appliance can also turn out tasty, non-alcoholic slushes for the kids.