Okay, that title wasn't particularly clever, as it doesn't include third person and it's not even the right words, but hey. I though using "scream" might imply something slightly different than the actual topic, which is:
Point of View!
Let’s talk about this. This is one of those things that, when you think about it, is generally pretty common sense. The problem is, I think people get so caught up in telling their stories and trying to get all the information out there, they don’t always think about it.
Some people have only a little trouble with this- a couple slips here and there, just something to keep an eye on. Some people have no trouble. Some people have lots of trouble.
The easiest place, in my experience, to have no trouble, is when you’re telling something from a first person POV. Because in first person, it’s pretty easy to tell what belongs and what doesn’t. Even when you’re not thinking about it, when you’re writing you generally know you can’t switch to someone else’s thoughts if your narrator doesn’t know them, unless your narrator is psychic. I think even if you weren’t paying terribly close attention, you wouldn’t make a mistake like:
“I was sitting at a booth and watching the bar door when my dad strolled in. He saw me and grinned.
‘Hey dad!” I gestured for him to sit down.
Behind Elsie, Frank watched jealously, sipping his coke and thinking of the best way to get her alone.”
First person is probably (certainly?) the easiest way to get close to your main character. It gives them a very distinct voice that builds their character, instead of just basing it on their actions. But of course, it can be very limiting, because you know your narrator so much better than anyone else (unless you play around with how you use the first person. See: Sherlock Holmes, for example (but really, see them. The real, Conan Doyle stories, I mean. They’re amazing). Watson is the first person narrator, but the stories are, of course, actually about Holmes).
Third person is where it gets tricky, because there are so many ways to do it, and people try to combine them. Pick one.
An example: The Harry Potter series, with a couple of exceptions (generally one chapter in the beginning of the book that shows what Voldemort’s up to) is told in close third person, close to Harry. We don’t know anything until Harry does (well, we might figure stuff out faster than he does, but only based on the information he knows). The story does not, all of a sudden, follow Hermione for a day or an hour, even if what happened to her was important. We have to wait until she tells Harry about this. This is a drawback of close third-person (it would be really convenient if the narrator could just show/tell us what Hermione did), but it’s necessary. By not leaving the one character’s side (and mind), we know them intimately fairly quickly. It’s similar to first-person in this way; it’s an excellent way to really develop your main character. Of course, it’s also more of an effort to develop the characters you’re not close to. But (clearly) every POV is a give and take.
I've seen more problems with this than one might expect. A close third person narration will suddenly switch to a different character, which is horribly disorienting.
To sum up, don’t stray. Switch, coherently, if you’d like, but don’t stray. Pick a point of view and be true to it, even when you’d like to let us know a bit of information that’s going to be hard to work in. It can be frustrating, but it’s worth it for a polished, coherent, smooth read.
This is more a call to double check your work than anything. I know that most writers know the differences between POVs. But like I said, sometimes it’s one sentence of slip-up, or just a switch that’s a bit disorienting. Make sure you know exactly where you’re going with your narrator’s voice, and make sure everything fits.
Hope this can help, live long and prosper and all that,