I've mentioned this in reply to a couple of questions. Time to post it here. For complex processing procedures such as color film or prints, you can help to eliminate errors by making a simple tape recording of the whole process in which you tell yourself just what to do and exactly when to do it. Tape speeds are quite consistent, so you can index times to the nearest second and be confident that they'll remain accurate. Then, when you're ready to process with all solutions at the correct temperature, run the tape and follow the directions. No timers to reset, and no instructions to look at.