I always carry a notebook and 3 pens in my pocket. Why? Having a quick, easy and accessible way to take notes is invaluable to anyone, regardless of age, profession or interests.
The notebook is a simple pocket notebook you can get from a discount store, and my pens are a four-pen, a black pen and a blue pen. Why three pens? One for yourself (four-pen), one to lend to someone and one in case another explodes.
My notebook contains a variety of things, from the idea for this post to the profits raised a recent fundraising event I helped coordinate. Get in the habit of writing notes and picking up your notebook in the morning and putting it in your pocket. Keep it next to your phone and wallet if that helps.
But how does this apply to ATC? Having a notebook next to you outlining your approach procedure for North, South, East and West arrivals can be helpful when controlling approach; and drawing out pattern work to see potential conflicts is a great strategy for Tower controllers. Or even as a pilot, write down the crucial details of your flight for easy reference.