Follow along with images and description below for the most comprehensive tutorial.
Take the end of the yarn from the skein (bundle), but don't cut it yet, just keep pulling until you are done. Start to wrap it around 2-4 fingers, depending on how large you want them to be. I generally like to use three fingers.
Wrap it around about 20 times. The larger the pom (more fingers you use), the more you'll want to wrap it around. 20 times makes a fairly full pom, with my three fingers. If I was making a larger one, with four fingers, I would probably wrap it around at least 30 times.
When you're done wrapping, cut the end off from the skein.
Then cut another piece of yarn (about 10 inches long) and wrap it around the bundle, between your fingers (see the images for help).
Then tie it, pull it tight to secure the bundle, and slip it off of your fingers.
Make sure it is pulled as tight as possible, and knot it again.
Then take your scissors and trim all of the loops.
Lastly, trim to even it out! There you have it!