Prepare drink(s) in shaker. Add cheap ice. Let sit for a moment. Moisten rim of double old fashioned glass with spent lime half. Twirl rim in salt. Put king ice cube in glass. Shake shaker until you've got frost or condensation outside. Pour into glasses. At some point taste and adjust for tartness with simple syrup. We use at most a teaspoon of syrup. Margaritas need to stay tart.