I'm going to piggyback off this comment as it touches on visualization, a concept I find that cannot be brought up often enough in monochrome photography. BTW, I find all the above comments workable and likely quicker in some instances. They are simply not the way I work.
Originally Posted by cliveh
I treat portrait, studio, etc. all as landscape, if narrower in execution. While it may seem more complex at first, using your spot meter to identify luminances you want to present in your final print, will give you power over light as no incident metering will. Meter your shadows and highlights the same as you might when shooting landscape, placing where and to what value they will be. Deepest shadows may be on background, a dark article of clothing, under the chin, or in the hair, all dependent on your subject and lighting. Highlights may be placed in same manner. The only difficulty becomes in properly registering skin tone, if that is your goal. That will vary upon race and season, as previously mentioned. Guess what? By using your spot meter and translating your decisions to the final print, you get to decide, dare I say "artistically", how your subject is presented.