Cut lime into small wedges (about 6-8). Place half mint leaves, half the lime wedges and a teaspoon of brown sugar in each glass. With a spoon or pestle or other club-shaped object to crush the mint leaves and lime wedges and combine with sugar.
Add crushed ice to the glass and pour the rum over the ice (half of the measurement to each glass). Add carbonated water and stir. Give the mojito a taste and adjust rum or sugar content as needed.
To make crushed ice: I froze water into ice cubes, then placed the ice cubes in my kitchen blender and pulsed it a couple of times until I got some finely crushed ice and some larger chunks. No need to be fancy, just put it in there.