This dialect question brings to light something very interesting about close third person narration: it mixes voices.
What are these voices?
It's easy to think of dialogue as voices, because when our character says something we get to put it in quotes, and write down exactly what it was that came out of his/her mouth. We can contrast the voice of one character with another.
- "We'd like to smack that calm right off him."
- "Oh, crap. Tabby, hon, let me look at you."
- "Fool sheep, putting me to this trouble!"
These are essentially the reported thoughts of the point of view character. Some authors put an internalized voice in italics, or go so far as to label it with the phrase "he thought" or "she thought." I don't, because I want really close point of view, and don't want to use filter words or other stylistic indicators that we're "switching into" someone's thoughts. However, the internalized thoughts of a character should match with that character's established voice, and this includes dialect. If anything, the dialogue should be more responsive to surrounding social context than the internalization, because how often do we censor our inner thoughts?
- Handing over money shouldn't take this long. All-they'd have been home by now if not for one soul-dark Higher.
- She's dark, fact. Like a sock to the stomach after how long I spent cleaning out that weird 'test population R' malware she straggled in with.
- One lamb from the seaward field was missing. Not caught in the fence, nor mired by the stream. Fallen into the sea? Not possible, since the tide was out, with no water in sight across the sunset flats.
3. Internalized Dialogue
Yes, there are some cases where you'll combine 1 and 2, directly reporting the internalized thoughts of your character. In my own writing, these are the only cases where I use italics for thoughts. You can often recognize them because they'll be in present tense (because a character is thinking about what's going on right now) even though your general narration is in past tense. In first person present tense, they typically don't need any special markers.
It's only a fool makes trouble on payday.
How's that! Maman doesn't have a complete shield in her collection yet.
This is the voice that tells you what the character is doing. How it's handled will depend on where you place the narrator. A first person narrator who is reporting from the action, or immediately thereafter, will typically match the voice of the dialogue and internalization. A first person narrator who is reporting from a retrospective distance may sound different - as, say, when an older person is reflecting on the events of her/his young life. A third person narrator is to some extent always external to the character. However, a dramatically distant third person narrator can be someone with a completely different voice who isn't even from the same world as the character. By contrast, a very close third person narrator should match the tone of the whole, but can be more problematic to manage because it must be kept distinct from internalization. Who here refers to themselves in the third person?
- He ducked and pushed in, work's-end hands adding to the layer of grime on the door.
- I look up, into the adspace.
- Corise trudged the shore, calling, dried salt crunching on the grass under her boots.
The Question of Description
Descriptions are tricky. Which voice do they fall into? In fact, as the author, you get to choose. Certainly you can make the descriptions part of your narration, and voice them accordingly. If you're describing anything that the point of view character would be incapable of perceiving, that's definitely what you have to do. On the other hand, if the point of view character can perceive it, then you can choose to put the description into the same style as internalization (and there's some description in my examples of internalization, above). When you're working with extremely close point of view, or Deep POV, you want to make everything internal to the character if you can. So imagine how the character would perceive this place or thing or person, and how he/she would describe it. Use the voice that you use for internalization, and make sure that your character's judgments are coming through.
When do I switch voices?
You're probably doing it without thinking, all the time. It's not something that happens without some kind of marker, but switches don't always happen between sentences. You probably could go into your work right now and find a sentence that switches voices in the middle. Maybe you've been writing along and you get to a sentence that really feels like it needs something, maybe a dash, or even just a comma, some way to show that the two parts of the sentence are separate from one another. The reason behind that instinct could be that you're switching voices.
Do I really need to worry about this?
Chances are, you don't. It takes a particularly challenging kind of narrative (like the one I'm working with now) to be difficult enough to require conscious thought. On the other hand, I always find that some conscious awareness is helpful. If you start thinking about these voices, it might help you tease out the reason why one punctuation seems awkward and another doesn't, why a particular passage isn't working the way you wanted, or why your instinct (or your critique partner) is telling you to use slang in one place and not in another.
It's something to think about.