I use to expose grey cards and then have someone plot the results with a densitometer. Now I simply expose a couple different subjects that are close to home or use a simple set up with a grey card, new white and black lace blouses or cotton shirts. Expose three sets of negs, 1/2 stop difference 3 stops each side of mfg ASA using my spot meter to determine initial exposure. One set gets normal development, one + and one -. I do this for any new film, developer (if I intend to use it extensively), shutter/lens for LF or camera body for 35mm.(posted 8260 days ago)When i first did this I would make 5x7 prints of each roll and then paste them to a poster board as a kind of ring around matrix to help me better understand relationships between exposure and development time with regards to final negative densities. A teacher I had in college suggested this and I think it is an excellent exersice for beginners in the darkroom.
Now I can pretty much determine my results with the negs on a light table and just a couple of prints to verify the look I want.