Juice the lemons until you have 1 cup of fresh lemon juice.
In a pitcher, combine the lemon juice and sugar.
Stir the mixture until the sugar is completely dissolved.
Add 4 cups of cold water to the pitcher.
Taste the lemonade and adjust sweetness if necessary.
Chill the lemonade in the refrigerator for at least 30 minutes.
Prepare serving glasses by filling them with ice cubes.
Pour the chilled lemonade over the ice-filled glasses.
Garnish each glass with lemon slices and mint leaves if desired.
Serve immediately and enjoy your refreshing lemonade!