Gilbert (AKA Mor'kil, of Carrion Crown fame) has written a neat article with a detailed set of instructions for making your own adventure journal:
Half the fun of rolling dice with your friends is keeping organized notes, right? RIGHT?!
And if you’re the DM, you have no choice but to write down every nuance of every NPC you’ve ever created, because without fail, your druid gnome is ALWAYS going to ask you about that one guy, in that one tavern, who made NO difference to any aspect of the story. We all know you’d rather smite that forest-dwelling hippie with a well placed tarasque tail than answer his insipid question, but being the fair and loving overlord you are, you flip through your trusty compendium of knowledge and reply with a hearty,
“His dog’s name is Mr. Woofers.”
Faced with this inevitable struggle, why not have a cool, new notebook for every adventure?