Before you get into making the cocktail(or mocktail), note that you can either mash your fresh fruit or berries with your muddler in a bowl or your cocktail glass. Or you can puree them ahead of time in a blender or food processor. I usually puree mine ahead of time.

• Place roughly 2 tbsp of fresh fruit or berry puree into your cocktail glass of choice, then fill the glass with ice and set it aside until ready to use. 
• Place 3 mint leaves in your cocktail shaker, and gently crush them with your muddler; you don’t want to rip or tear the leaves, just crush/bruise them to release their fragrance. Add the white rum(omit if making a mockail), lime juice, and simple syrup(if using) to your cocktail shaker, followed by a few ice cubes. Cover and shake for about 10 seconds. 
• Pour your cocktail(or mocktail) mixture into your glass of ice(if your cocktail shaker doesn’t have a pour spout, you can pour the mixture through a fine-mesh strainer.) 
• Top your cocktail(or mocktail) with club soda, then garnish with a fresh sprig of mint, a piece of fruit or a berry, and/or a lime slice.
• Serve and Enjoy!