From Unpluggd today, I learned about The Breadbox Test, a clever way to sort out what gets tidied and how. Essentially, anything smaller than a breadbox should be put away:

Things like pencils and paper clips get tucked into a drawer, while larger items like your drawing tablet, reference books or a potted plant stay seated comfortably in plain sight on your desk top and shelves.

I would suggest that some small, but oft-used, items could just have a smart place to go, like a few pens or pencils in a jar on the desk. But within reason: not every pen, pencil, and marker in an old, rusty, giant coffee can.

I would also suggest keeping knick-knacks, gewgaws, and other doodads to a bare minimum. A few mementos might be nice, but in moderation.