In all my years fishing, I think ive only documented a couple pages of notes. Keep telling myself to get a journal and write down every trip, if for no other reason to look back on and remind myself how bad the fishing is getting...

For the beginner it can speed up the process of water height/clarity and color/size recognition for those conditions.

I second the Excell spreadsheet, you can customize it to your needs.. Date, River Locale, water height/temp, lure used, fish caught, etc...