I usually take a good look at the negative in light before I print and make an educated guess as to what f-stop and filter to start at. Assuming it's a good negative, I start at a 2.5 (I like my prints a little contrasty) and then make tweeks in time, etc. If I'm pretty confident in my exposure, then I make a test print with a couple different times to get my exact exposure. It works pretty well for me.