Squeeze the juice (or use a hand juicer) from the lemon into a quart sized mason jar, a shaker, or anything else you can fill and cover tightly. It just needs to be at least 16 oz. Toss one half of the lemon in with the juice.
Add the sugar
Fill the jar/cup/shaker with 1 1/2- 2 cups of ice. Basically, you just want to fill it up to the top.
Add enough water to cover the ice
Cover and shake briskly, until the sugar is mostly dissolved. It will actually turn into this wonderful, sweet "sludge" at the bottom of the cup. Drink straight from your shaker or pour into a glass. Just make sure you get all the sweet goodness out of the cup!
For a nice extra touch, serve in glasses with a sugared rim!