Regarding cluttered and messy NA lists, here's how I have solved it:
I wrote my next action on post-it notes. I then took an A4 piece of cardboard (the back of a pad of paper) and stuck the post-its on that, side by side. Each post-it has around 8 NAs on it. So when some of them get crossed out or changed, I only need to re-write the rest of that post-it, not a whole sheet.
Also I sometimes write a header on each post-it: "Phone", "Talk to boss", "Ultra urgent" etc.
The piece of cardboard lies next to my computer all the time. I put it in a clear plastic sleeve so it doesn't wear out and the post-its don't come loose.