1. Just before serving, in a half- gallon pitcher combine the tequila, the minimum amount of triple sec or Cointreau, water and the lime juice concentrate.
Taste and add more of the orange liqueur if you think your margaritas need more sweet oranginess to balance the other flavors. Remember, you're tasting it warm and undiluted: when chilled and diluted, the flavors will be mellower and the lime's tartness will be more compelling (tangy, warm champagne is not nearly as inviting as ice-cold). .
2.Pour several tablespoons of lime juice onto one small plate, several tablespoons coarse salt onto another. Have martini glasses at hand (for an extra special touch, you can chill them).
I like the 5-ounce size, since that size drink will stay cold from first sip to last. As your guests ask for their margaritas, invert a glass into the plate with the lime juice to moisten the rim, then lightly dip into the plate with the salt. For each drink measure 2 ounces (4 tablespoons) of the margarita mixture into a cocktail shaker I can do 3 drinks at a time comfortably in mine.
If you have a 2-ounce ladle that you can keep in the pitcher, measuring goes much faster. Add ice cubes (I put in 5 cubes for 1, 8 for 2, and 10 for 3). Secure the lid and top and shake vigorously for 10 to 15 seconds.
Strain into the salt-crusted glasses and hand off to the lucky recipients