I Always start with a graycard test. shoot a gray card, develop film, develop paper so that the Original gray card and the dried paper gray card have the value. Take the next negative and print it at the time of the gray card paper development time found (a blank part of a negative should be just at maximum black at that time). It will show if it is right. This method illuminates all variables between picture taken and print.
I do nearly the same, but a bit differently. I'll meter a grey card with the meter set at ISO 100 (for a nominal ISO 100 film), then shoot a sequence of -2 down, -1 stop down, as metered, +1 up, +2 stops up, to span the entire ISO range from ISO 25 to ISO 400. Then shoot a couple of frames at f/22 at 1/1000 with the lens cap on, to get some totally unexposed frames. Develop. Put a blank frame in the enlarger at the height you would normally us, and do a step test to get a series of exposures across the paper. Develop the print and find the time that gives you maximum black. Then put the negative shot at ISO 100 into the negative carrier so that the image on the paper shows part of the frame shot at ISO 100 and part of the frame shot at ISO 50, with the blank area between the two frames in the middle. Expose the paper for the time you found from the step test, and develop and dry. Ensure the middle strip on the print is as black as it should be, and see which of the two frames for ISO 100 or ISO 50 matches the grey card. If both are too dark, make the same print with the negatives for ISO 200 and ISO 400, to see if either produces a grey that matches the grey card. You could even do a test for the ISO 50 and ISO 25 exposures if need be. Once you have a ballpark idea, you can shoot a few more frames at 1/3 stops on either side of the ISO you've identified, to fine tune.
The only thing to remember is that you're using the fact that the max black on the print matches the max black from your step test to decide that you've got the correct paper exposure timing. Of course, once a paper hits max black extra light doesn't make it any blacker, so it's possible to unknowingly err on the side of overexposing your test print. To double check, once you've got it all dialed in, shoot a frame at your arrived-at ISO, develop, and print with the inter-negative space on the print but use a few seconds less exposure time on the print. If the space that should be max black comes up a bit less than max black, you know you've got it right.
All that remains is to see how the highlights come out in a full-range subject, and adjust developing time of the film as necessary. Yes, that may change the grey tones somewhat too, so a little tweaking will be required. But the advantage is that in the end, you've included every element of the image: film developer, development, exposure (including any effect of the film base itself), illumination of the enlarger, enlarging lens and paper developer.
