My photo teacher started us out taking field notes on every F stop and shutter speed. Since we were shooting B+W negative film with something like 10 stops of dynamic range the usefullness of such notes was limited. I think something else like EI for the roll and development time are more critical.

Once I start shooting more slide film I'll probably take notes that say something like the "metered LV" but more importantly how much I chose to deviate from the reading based on the scene in terms of stops. That would probably help more. Though these days with these zone system 3D matrix meters built into any 35mm camera there is less and less need. Maybe I might record especially long exposures to figure out reciprocity of various films. Of course the problem with buying whichever film happens to be the cheapest is that you always have a different film.

One problem I had was that I learned to shoot color on digital (blah) which made me mad because I'd start losing color saturation around zone IV, which would make me underexpose until I saw the correct colors on the LCD and add a curve to the images in "photoshop". This procedure does not work with color slide film. I had such a bad habit of instinctively pulling the exposure back on every shot that all my slides come out uniformly underexposed.