I place adhesive mailing labels to the film holder listing exposure info, film ei, filter used and development required and the date. I will usually make a notation about the location in a notebook at home with the corresponding file number for the neg. I will also record the date and location of any neg
I keep on the margin of the negative if it is sheet film. I will also record in the notebook the developer details.

In the darkroom I try to tape record important information and then later sort out and record the important stuff on the back of a proof print. I will also use a marker and indicate on the proof areas that have been burned or dodged, with what filter and by f-stops.