I've changed my process over the years. I used to do all my first drafts longhand. This was back when laptops were first hitting the scene and carrying around a pen and notebook was just way easier than lugging around a computer. I eventually had to give up longhand rough drafts for time and carpel tunnel's sake. Now, I do all my notes, plotting, and preliminary work in notebooks and all my writing on my computer.
Why in this increasingly paperless age do I stick with pen and paper at all? Part of it is tactile. The pen flowing over the page makes me happy. It's certainly not for clarity. My handwriting is just atrocious (not an exaggeration). It's actually difficult for me to read some of my notes due to the deranged nature of my penmanship. I do love using the icons I've created over the years: huge arrows and asterisks to indicate important notes, sad faces when I've said something stupid. My ability to take notes, mark up, and cross out (but note delete) info helps my brain sort out the wheat from the chaff.
But the real reason why I use pen and paper is because it is a habit, and sometimes that's the most important thing to a writer. Crutches, ones that don't hurt your creativity, productivity or health - I'm looking at you alcohol and junk food - can be a huge boost to a writer. I LOVE hunching over a pad of paper and scribbling like a mad woman, preferably while sipping on coffee and listening to experimental music. Does it help me? I think so. Writing is slower than typing and it forces my brain to slow down even when it wants to fly off the handle. It gives me something physical I can flip through and something portable but not ever present. And a notebook is a visual reminder on my desk that I need to get things done. But even if it doesn't help me, I still love it and will continue to do it. :)
What habits do you hold on to?