First prepare the Margarita and put in the refrigerator to keep cold, then work on the shrimp. The recipe works best if you sample the margarita as you prepare the spicy shrimp. Be sure to leave at least a 1/4 cup for the shrimp or you will have to make more margaritas. Depending on how much you have sampled you may want someone else to tend to the grill. And, as always, don't skimp on the quality of tequila. Oh, and the shrimp is phenomenal!