Small, big win -- get multiple colors of pens.
I found nice packs of pens in Morocco that contained one each of a black, blue, green, and red pen. I bought five packs.
Incredibly useful. My system:
Black -- big details, big picture.
Blue -- specific notes, little details.
Green -- complete, or on-track and doesn't need attention.
Red -- next up, urgent, unacceptable, or needs attention.
It makes is easy to skim notebooks rapidly. I can look at the black ink if I want to figure out what's going on, can skim over anything blue unless I want details... if I'm in a real hurry, I can just look for what's red and do that. If I want to see progress/timelines, diving into a mix of blue and green will give me that.
Very useful. I find paper next to the computer to be a huge boon anyways, and multiple colors of pens makes even doubly useful.