I often have one notebook that is devoted entirely to a project or part of a project. The project develops there in pen and ink; bibliography takes shape there. Right now I have one notebook that is devoted only to planning the summer's work and another devoted to planning the "year of reading Latin American poetry."
I wish that I could redevelop the ability to write actual prose by longhand rather than typing. I cannot shape whole paragraphs in handwriting any longer. I'm sure my writing would improve if I had that extra method.