Wrap your first yarn around the base structure/datebook about 10 times. Clip it off with some scissors, and wind some other yarn colors over the first layer of yarn, say another 10 times, clipping off after the tenth wrap. Layer on a few different colors. (You can make pompoms of one or many colors, of course!)
After you've got all the colors that you want wrapped on, insert your finger between yarn and the base you're using to wrap around. Insert a 4" or so piece of yarn where your finger is and tie into a tight knot. Turn it over and do the same on the other side. Remove from base. Then cut a string about 12" long, and tie both halves together in the middle, where your other ties are.
Turn the object on it's side where you will see loops. Insert scissors, and cut all the loops open. Repeat for the other side. Fluff the pompom up so it's round. Then holding by the long piece of yarn, clip the outsides of the pompom so it has a nice round compact shape. Clip it over a cloth if you don't want the little scraps of yarn to scatter everywhere. Make a few while you're in the mood and have all your supplies handy. Amuse your cat. :)