Over the past 5 years I have been sketching compositions on paper. Sometimes they are detailed, specific outlines of what I imagine for the music, sometimes they are how I would like a synth to sound, sometimes they are me thinking out loud about the structure of the music I am working on.
The main reason why I do this is because it is a way for me to problem solve away from the computer. I find the computer is so powerful at trying things quickly that it can get in the way and overpower some of my decisions.