1. Split it in half horizontally by gently piercing it with a fork all the way around and then separating it.
2. Butter it (optional).
3. With a sharp knife, section each half into quarters and, depending on the size of the muffin, split each quarter again. Now you have sixteenths.
4. Eat the sections with a fork.
I would never dream of doing this myself. It would look too silly.