There are a few pros to a center pull ball:
1.) You can pull yarn from the inside and the outside at the same time
2.) Your yarn stays protected inside more yarn
3.) your ball of yarn will roll around on the floor less keeping your yarn clean, and it won't become tangled around furniture.
How to start
first you want to find a place to hang your hank of yarn. If you don't have a swift or a willing partner to hold the hank the back of a chair or your knees will suffice.
Next take the dead end of the yarn and making sure it is about 10-12 inches long. (Your dead end it the end of your yarn and the live end is what leads back to your hank of yarn.)
Wrap the dead end around your thumb, making sure that the extra inches are hanging down the length of your arm.
Now you will take the live end of the yarn and begin to loosely wrap it around your index, middle and ring fingers or how ever you winding a ball of yarn.
Continue to wrap the yarn around your three fingers until you see a ball start to form out of the wrapped yarn. Slip your fingers out of the ball of yarn and continue wrapping the yarn around itself, being mindful of where the dead end of the yarn is attached to the ball.
when you are finished your ball of yarn should look like this:
Ta-Da! A center pull ball of yarn.