OrgMode is great when I'm at a desk, but I want something I can use "anywhere".
So... What do you use?
An added benefit: Jotting down a note on paper appears to be more socially acceptable than taking notes on a phone (might be OK if you can touch-type on a touchscreen, but I can't). A notebook is self-explanatory.
For organization, I use some basic pieces from the Bullet-Point Journal method: A dot in the left column for general notes, a circle for events, a square for to-dos. Put a check in the square when done, an X if I decide not to do it, and a > if I've moved it to OneNote or something.
Recently I've been experimenting with the GTD system. Someday I'll write a blog post about it, but here's the gist: Thoughts go into the notebook as they occur, so I can get back to work/etc. Periodically I review recent notebook entries and move them to projects and project tasks pages in OneNote, then put next Step to-dos for each project in Wunderlist. It's a work in progress.
It's worth mentioning that the OneNote app in Windows Phone 10 is much improved over the version in Windows Phone 8.1 -- actually, it's exactly the same as the app version on Windows 10, and works just as well on the small screen.