There is only one rule in determining what the position of the narrator should be. It has to be consistent.
The narrator can be first person, third person or “fly on the wall” type, also known has omnipotent narrator, or could even be second person, by which the writer is directly addressing the reader.
Consistency does not necessarily means sticking to a single type of narrator all through the novel. There are ways to mix and match, yet, this has to be carefully done.
The golden rule is that each passage has to have a single type of narrator. For example, let’s postulate a first person narrator where the main character is the narrator called Jane.
“Jane is reading a guide book and we, as reader, are offered a peak into what she is reading. The guide’s narrator is a second person narrator. It says “When you reach the entrance of the cathedral, you will see blah blah blah …”. “
So there we have two different narrators in the same chapter, or even on the same page, but each has a very well defined position so all is well.
Now our Jane has entered the cathedral where she was supposed to meet her sister. It goes like this “As agreed with Lisbeth, I went straight for the chapel of St Andrew. Since I was already running late, I was very surprised not to find here there.” So far, so good.
Unfortunately, the writer had a bad day when he wrote that passage and he wanted to rush the plot forward. The writers knows the entire story and he needs the reader to know it too. So he writes “Unbeknown to Jane, Lisbeth car was crushed under the wheels of a refrigerated truck on the speedway, with Lisbeth still in it despite the valiant efforts of the rescue team.”
Here we have a problem. How could Jane possibly know something that is unbeknownst to her? The answer is simple. She can’t. That indicates an abrupt change in the position of the narrator. The writer has been careless and the editor has no choice but to strike it and demand a correction. The writer might argue that this is essential to move the plot forward, and he might be right, still he wil to find another way to do so, as unjustified changes in the position of the narrator are a sure way to loose your reader.
Nobody ever said that writing was easy 🙂