One of the constant challenge of writing with multiple POVs is to determine which one should narrate each scene. I'm an advocate of stability in POVs - that is, I try not to change too often, so that the reader has time to get comfortable with each of my POVs before I move on. I also try to have as few of them as I can.
In any given scene, however, I may have more than one POV character. Sometimes it seems obvious who should tell this part of the story, but that is not always the case. Last year I read The Power of Point of View, from Alicia Rasley, and she had some questions you could use to help yourself determine who to pick.
1. Who has the goal in this scene? This character will drive the action in your scene. Often, he's the obvious pick (which doesn't make him a bad choice, far from it). He wants something, and will do what he can to get it.
2. Who has the more at stake externally/internally? Narrating from the POV of the character who stands to lose a lot will raise the tension in your novel. Remember the last post about raising the stakes? It's true for single scenes, too. Bring the reader close to the character who'll care about what happens, and they'll be more inclined to care, too.
3. Is there someone with an intriguing perspective? This can be the character who's a total stranger to the world around, who clashes with his environment. It can also be someone with a special way of saying things which will make the scene a distinct experience. I'd be careful with this one, however. I know extravagant POVs tire me after a while.
4. Who has a secret, and do you want the reader to know? This one is fun, but should not be abused. Sometimes you have a character with a secret, and using him as a POV can help build tension. Getting the reader to guess about the secret will create an interactivity with the scene.
5. Who is not revealing his personality through dialogue and action? You don't need to be into an upfront person's head to get to know him. They'll blurt out anything they think (a problem my characters all have in the first draft, but that's another matter). Sometimes, it's more interesting to use the POV of a character who smiles when he's angry and says thanks instead of an insult.
This isn't an absolute guide, far from it, as choosing a PoV will depend on the current circumstances. These questions help me a lot, though, and I can get through most decisions with them. And when it's not enough, I fall back on my usual trick: I write super-quick draft scenes of both options, and pick the one I like best.