There are many different ways to make a pom-pom but I'll show you a couple here. The primary method I use is a clover pom-pom maker. These come in different sizes depending on what size pom-pom you want to make. If you don't have the right size you can either trim to size or use a DIY method that uses circles of card.
Now for the Clover pom-pom.
Why not try this Pom Pom technique in these patterns: