To add to what Pam said about deciding about whose POV to use in a scene, I'd always gone with the maxim of using whoever has the most at stake in a scene to choose the POV. If Clark and Lois are out on a date and the restaurant catches on fire and Clark has to pull a Superman to rescue everyone, chances are Clark has the most at stake - the possibility of a big reveal - so it makes sense to use his POV. If Clark and Lois are out on a date and Lois spots her old boyfriend, the one that knows that she once got drunk and danced topless on a bar and Lois is afraid that this guy will tell Clark, it makes sense to show the scene from Lois's POV.
As for changing POV from scene to scene, that is exactly what I do. However, the other maxim that I've always followed is that the only time it is OK to change POV from person to person within a single scene is during a love scene. Because you want to be able to show how each person is feeling and reacting to the other, it is OK to go back and forth between POVs as long as they are in different paragraphs and you make it clear who is feeling what and avoid roaming body parts. Kind of an action/reaction thing - Clark loved the feeling of Lois's soft lips against his own. Next paragraph: Lois couldn't believe how bold Clark was being, but she liked it.
This discussion just gets more and more informative!
Lynn
