Once you've folded your cardboard piece in half, start wrapping your desired yarn around and around the cardboard, again lengthwise.
The more times you wrap the yarn around the cardboard, the more full and thick your finished pom-pom will be. There's no right number of wraps to make a pom-pom.
If you're making a project with multiple pom-poms, you might want to count how many times you wrap the yarn so that all of your pom-poms end up looking the same.
