I use the classic spiral notebook and I keep a pretty detailed log of my printing. I shoot mainly large format but also medium as well. I have a field notebook in which I record exposure information for each sheet. I do a quick line sketch of the scene so I can record the placement of the different zones. I only take notes on each roll if necessary (e.g., the whole role is to be developed N+1).
These notes are necessary for developing the film, but in addition, especially when you are still learning, detailed field notes really help you to understand the relationship between exposing, developing, and printing. Not that I am an expert, but my notes are really helping me.
In the darkroom, I can refer to previous notes on similar negatives to get a starting point for aperture/contrast/time, and it definitely saves me both money and time. I start each printing session in the notebook with the date, and a referral back to my field notes on the negative (e.g., March 15, 2008 - negative from March 1, 2008 - sky and shoreline). I record the information for each test print, both in the notebook and on the back of the print. I use a soft artist's pencil to write the info before printing. You can't do it when it is wet, and by the time it is dry, you forget what the hell you did anyway. If the information gets too long to write on every test print (e.g., complex split printing or dodging and burning), I just write a number and a date that refers me to the notebook.
This may all sound pretty nerdy, but trust me, I find this invaluable as a tool for learning. When my test prints are dry, I can sit at the kitchen table and look over all the different stages and possibilities, with notes on the negative and on the prints, and make sense out of the various change or approaches from both an aesthetic AND a technical viewpoint (the two have to come together at some point). Things always look different the next day, and not just because of dry down. Keeping good notes doesn't just save you money (hit and miss with large format gets really expensive). More importantly, it helps you keep control over what you do so you can produce what your imagination sees.