In 35mm I've been practicing with an 85mm Jupiter-9 M42-mount lens (it's a Sonnar clone from the former Soviet Union), mounted to either a Bessaflex M42-mount camera, or more recently a k-mount ME Super with an adapter (the aperture-priority of the latter makes balancing fill flash, if required, a bit easier for me).
I normally use Kodak BW400CN for this - I've found it holds detail very well - very hard to blow out highlights even if fairly close up with a flash. Also the B&W "creaminess" works quite well for many people, especially female subjects and children.
Recently I acquired a Mamiya C330 with 80mm and 180mm lenses. Last weekend I was experimenting with performance portraits using the 180mm lens and XP2 (locally BW400CN in 120 isn't a big seller, I'm told, so it's not readily available). The film is out for processing - I'm very curious to see the results.
Overall, I'm still in what I would consider an experimentation stage - I had a local part-time pro look at what I've done, and his main criticism was that often I don't get the subject's eyes perfectly in focus, which can be distracting in a portrait - while I prefer shallow DOF he suggested a minimum of f/8 is usually "safe". I've been trying to perfect that, I guess practice makes perfect
Also I've acquired a whole lot of Tri-X in 35mm and 120, so I'm probably going to try more portraits using that, as well...