I admit it. I'm a notebook jumper. It is rare that I fill a notebook to capacity before skipping to a new one.
Because I'm a little neurotic and slightly OCD when it comes to my writing (my family would tell you I'm nowhere near OCD in my regular daily life), I find it somewhat stressful to have several notebooks "going" at once -- which is what I've been doing. One notebook for short stories. One notebook for blog entries. One notebook for ideas. One notebook with novel bits in it.
If I misplace a particular notebook, a project goes missing for a while. Much easier, and more satisfying because I like to be able to see my work add up, to fill one notebook before moving on to the next. Not only do I have everything at hand and the freedom to write what I want, when I want, but when the notebook is full I have a testament to how much work I've actually done.
And when I stack up the filled notebooks...I'll have stacks.
So recently, I decided that I would be brilliant and use tabs to indicate when I switched subjects/projects within a notebook. Different color tabs indicate which project I'm on.
This seemed really smart at first, but then I kept forgetting which tab meant which project.
About a week ago, I'm complaining about my system to my friend John -- which is what I do.
He says, "Use a table of contents."
I say, "Nerd."
He says, "No, seriously. Number your notebook pages first thing. Leave the first page of the notebook blank. Whenever you switch projects, go to the first page, list the project and the page number."
I'm doing it. Though, I can't bear to lose even a page of a notebook, so I'm Table-of-Contents-ing on the cover of my notebook. I figure if I need something later it'll be good to just look at the cover and see what's in the notebook at a glance.
If you're looking to keep a writing notebook/journal, you should do it too. And you can even use tabs, so you can flip easily between projects.