Paper notebook. I wouldn’t recommend loose sheets of paper. :) After 15 years of writing notes on loose sheets I would start differently :)

Go Tim Ferris way - notebook where the first page is left for the table of contents, and number all even-numbered pages as first step.

I hate handwriting with a passion. I have my whole life. I have horrible handwriting and my hand gets sore 5 seconds after I start writing.

I am sure it is because I don't hold my pen/pencil correctly, but I think after 43 years I am not going to suddenly fix that.