You'll need lemon juice, sugar, water (not shown) and of course the container you'll be making it in.
To start off, you'll want to pour the lemon juice in your container. Pour according to how large the container is and how strong you want it to taste.
Next, you're going to add the sugar. Also add this according to the container and your personal tastes.
Just FYI, I added 4 oz of lemon juice and 2 tablespoons of sugar for a 24 oz cup.