You need is some card, a cereal box is the best ... scissors, wool, needle and a compass.
You need 2 donut cardboard rings. Mine measure 2 inches in diameter (outer ring) and 2cm in diameter (inner ring measurement)
Cut a length of wool, a manageable length (about 2 meters)
Cut around the rim of the donut. You should have enough threads going around it so that they don't come out when you cut it
Get a piece of thread and wrap it between the 2 cardboard rings. I wrapped around twice before pulling tight and tying off securely.
Your pom pom is now made, you will probably need to trim it a little and cut off the long tie threads.
If you want to make them into a garland though, take a piece of wool approx. 3m long. They need to be spaced equally along the garland so starting at one end, tie a knot in the wool