You’ve got your skein untied and ready to go. What’s the next step? Rolling your yarn into a ball.
Start by wrapping the yarn in a figure 8 around your thumb and forefinger.
Fold the figure 8 in half. (Does that make it a figure 4? Probably not.)
Then, start wrapping around the little yarn nubbin you made from your figure 8.
Wrap it snugly, not so tight that you have to put muscle into it, and not so loosely that it’ll just fall apart. Keep going until your proto-ball gets nice and chubby.
Then, turn it 90 degrees, and hold it between your thumb and forefinger. Wrap the yarn around the ball in the new direction, catching your fingertips as you go.
Keep going, turning the ball every 20 or so wraps. Turning the ball and wrapping in different directions will give you a nice round, even ball. Making sure that your fingers get caught every time you start wrapping in a different direction will ensure that you end up with a squishy ball of yarn. This will stop you from wrapping the yarn too tightly, which can end up removing all the springiness from your yarn (imagine keeping a spring stored in the stretched-out position, it would eventually stick that way).
When you finish, your ball of yarn should be firm enough to hold its shape, but loose enough that you can squeeze it like one of those foam stress balls.
Tuck the end of your yarn around the last group of wraps, and your yarn is ready to go into storage. Or, cast on and start knitting!