Pick a good amount of mint leaves and place them in a highball glass (use more than you think you need. Somewhere around 12)

Juice a lime and add one of the halves to the glass

Use a muddler(or the back of a spoon) to express oils from the lime and mint(you want to bruise the leaves but not pulverize them)

Add 2 Oz of a good white rum(this is the star of the drink so make sure it’s good. I recommend Havana club if you live outside the US.)

Add 3/4 Oz of the lime juice you squeezed earlier

Add between 1 and 2 Oz of simple syrup, depending on how sweet you want it to be. (Personally I go for 1.5)

Add ice and stir until the glass is uncomfortable to hold(about 60 seconds)

Top with club soda until the glass is completely full

Add a straw and garnish with a lime wheel and a mint sprig