I've been journaling and diary-keeping for many years, but I really got seriously into it in around 1998 or so. I've used both paper and digital journaling (I was on Livejournal for around 10 years, until it jumped the shark) but now I mostly use paper.

I have three journals on the go at the moment. My most important one is a bullet journal, though I have diverged from the "official" format and work mostly in weekly spreads. I find that it helps my ADHD brain keep track of the structure of my week better. For this, I use an A5 dot-grid book. Weirdly, although I'm quite artistic, I keep my journals minimalistic and mostly un-decorated.

I have a daily long-form journal, though in practise I only write long entries a few times a week rather than every day. I'm into the Tarot too, so I also use this one for my daily card pulls and weekly/monthly spreads. For this I use an A5 lined book, because I fill them faster and lined notebooks tend to be cheaper than dot-grid ones.

My third is a Commonplace book; this is where I keep a record of things I've learned that I want to remember, books I'm reading (and my thoughts on them), quotes I want to keep, notes about research I'm doing, and stuff like that. I use loose-leaf binders for this, so I can more easily rearrange pages and keep entries on specific topics together.

How about you?