First, thanks to Sandi for giving us a chance to get together.
To take the last question first, Jill, I'm afraid there are no rules. Omniscient narrator is not wrong, but . . .
If you're writing from the omniscient narrator, you lose the opportunity to use wonderfully subtle tools for creating characters like describing things in language that reflects your viewpoint character's state of mind. Avoiding omniscient narrator also allows your interior monologue to flow naturally, without all those awkward mechanics, like "he or she thought," italics, or shifts to the first person. It's not necessary to use first or third person -- Jane Austen created some brilliant characters in the omniscient narrator -- but it is easier.
I've sometimes seen the omniscient narrator used extremely effectively. Consider the first chapter of Harry Potter and the Sorcerer's Stone. But J. K. Rowling then moved to the third person to let all her readers fall thoroughly in love with Harry.
Debra and Jeannie, I'm not entirely sure what "deep" POV is. I've always thought of the third person POV as being an intimacy/distance continuum, running from something close to omniscient narrator at the distance end to something close to first person at the intimacy end. One of the elements that locates your point on that continuum is the language you use -- including the names your viewpoint character uses for himself or herself and for others. At the intimate end, your character might refer to her father as "Dad." A little further toward the distance end, it might be "her father." Just try not to change distance too abruptly -- by using two or more different referents in the same scene, for instance.
My website, http://www.davekingedits.com/, has an article that goes into more depth on POV.
Hope this helps,
Debra, I will answer your other question in the next post. ~Sandi