Pencil and paper here. I tried OneNote on my Windows laptop and found it too inefficient. I write notes in the margins, at odd angles, use stars and circle phrases to highlight important points, draw arrows to connect related thoughts, and all kinds of chaotic looking chicken scratching. If I'm still having trouble with something a week or so before mid-term exams, I'll open up Word and type up my notes in an outline format. If I need more help I use Powerpoint to make slides to use like flash cards. I may make the move to Pages and Keynote this quarter, though.