One thing that has helped me keep to start keeping long-running notebooks (which I use as engineering notebooks at times, among other things) is to actually keep two: one for immediate notes that I treat as disposable, and then another for "permanent" stuff. The former is a little 3x5 pocket notebook that literally lives in my pocket (or beside my keyboard), and I can jot stuff down in whatever order or format is convenient at the time. When I have a bit of time, I go through and "reconcile" the smaller notebook with the larger one (a regular composition book) by copying over the relevant information and indexing it. I then cross off the pages in the pocket notebook so I'll know I've dealt with them. (FWIW this is inspired by the bookkeeping practice of keeping a "wastebook" or "journal" that is just a list of transactions as they happen, and later "posting" or reconciling them into one's ledgers.)

This has a couple benefits. First, you always get better work if you go through more than one draft. Second, the idea of something being in the "permanent" notebook forever can cause me to freeze up a bit, not wanting to "mess it up". Having a place where I can "stage" or draft my entries helps with this.