Patrick Lucas Austin, LifeHacker:

There’s a pretty straightforward reason you should attach a clip to your Apple Pencil: it lets you treat it like a traditional writing implement. The Apple Pencil’s completely rounded design means it is more prone to roll around your desk, or right off your table and onto the ground. In addition, adding a clip lets you, of course, clip it anywhere you’d stick a regular pen.

Have an Apple Pencil? Check out this clip for the Fisher Space Pen. $2, plus shipping (maybe buy a few at this price), and stick one on your Apple Pencil.