Peregrina Historiae has it pretty much laid out:
"Replace the Hipster PDA for a small moleskine or moleskine weekly agenda and the rest is pretty much the same… Particularly the Moleskine Notebook part (I have a lined one instead of gridded) and the switching back and forth between scribbling on a paper and typing on a computer."
Can’t get simpler than that.
I keep track of my ideas on paper (in a moleskine). I think that’s as simple as you can get!