Day-to-day sketches and TODO's and little note lists: I keep a spiral note book next to my keyboard. I'm a leftie so it's upside down. I use the blue Pilot Drawing pens in various thicknesses. They dry instantly, so no ink smudges. Nice.
In addition to these I keep a day-to-day diary in .txt documents on my computer, I just open them in Sublime text or vim and make a new one every month. I try to just write four or five lines about what I've done every day as well as what I need to do tomorrow.