I don’t use just one thing. It makes it hard and rigid if im not carrying this specific notebook around for me to write in. So, i use whatever i have at the moment. A piece of paper, a note on my phone, or the leather bound journal i bought for that purpose.
I use a few structured questions to which I try to answer when I journal. Examples: what went well today, what are you grateful for. What I found works for me is having it in a document which I can access both from my phone and my laptop, to me writing in a notepad or a piece of paper is strange as I do not do this so much in my regular life, so something that I easily accessible whenever I have the 5-10 mins to fill it in is great
I keep 3 different journals one for my thoughts and things I need to work through, one as a daily journal and one for gratitude. I make sure that the pen I write with feels great on paper and the paper I write on displays my ink in its most flattering colour. I do this so I get excited about writing. It’s a very tactile experience which I enjoy and that make it easier to write.