What would be going overboard in terms of informal or slang language? I have a character (wrongly) assuming another is carrying a weapon of some kind. Is it best to just say, "Thinking the person up ahead was carrying some sort of weapon," rather than the initial thing I thought of to say the same thing, which was "Thinking the person up ahead was packing heat"? I've read informal, or slang, before in other works. Hell, a large part of the reason why Stephen King rewrote The Gunslinger was to update the terminology and such, because it didn't coincide with the rest of the series, which had been published 10 and more years after the first was published. Question being, is "packing heat" too informal? (Though, the more I think about it, the more I'm leaning towards: yes, quite simply.)
If you are immersed in a character POV and using character-driven narration, the use of slang is perfectly fine, as long as the reader will understand it. In character-driven narration, you are narrating in the (inner?) voice of the POV character, so you will use a speech pattern and word choices consistent with your character. Generally, the narration is "cleaner" than dialogue, without breaking phrases or responding to other characters. But the voice is recognizably similar.
The narrative voice will vary from author to author and story to story. Some of my stories are told very much in the voice of the character, in which case "packing heat" would likely show up in the narration. Other times, I take a more detached approach, maintaining an authorial distance; in that case, using slang or informal language would be out of place.
It soely depends on how "in character" you are. If it's a first person story, then slang will most likely be very presnet and is generally more accepted that in third person stories. If it's in third person, you have to hink. Is this the type of character who would think it in that terminology? And have I established this character enough to use this type of phrases and make it fit comfortably in the plot?
It depends on what kind of character you have. Is the character someone who would think about that particular slang at that particular moment? Is this the one and only time this character has/is going to use slang in the whole story? Does this fit his/her personality?
I don't think anyone says "packing heat" anymore. Most people I know would just say he's "packing" or "has a piece." If he's a real "goon," (ganster or thug) he might have a "cannon" (large-caliber handgun) and if he's on a budget or likes to get personal with it, he'll have a "shank" (knife) or a "swisha" (switchblade). I listen to too much rap... And I agree with what everyone else said. Everybody talks/thinks in a different language. It's up to you to decide if slang is the language your character operates in.
AnonyMouse's post reminds me of another consideration. Make sure your slang is contemporary with your story. If your story is set in 1965, the term "bust a move" has no place in either narrative or in dialogue.
I was once reading a book written in the 70's and the language was so outdated that it made it difficult to read. Even if it is in context now, think about how readers will look at the narrative in 10 years or 20 for that matter.
Personally I would suggest you only use slang in dialog. Unless in first person, the slang would not be appropriate to me. Dcoin also has the valid point about timelessness. Some phrases do not age well. Its like the when marlon wayans was making fun of some educator or senator who suggested creating a slang dictionary to understand children. He suggested that a slang dictionary should be written in pencil so entries could be added and removed on a monthly basis. In dialog(my spelling sucks) slang is okay because people's minds, I believe, are able to accept that easier then in the other parts of the story
I like some slang use because it helps me get into the character's head a little more deeply. It really bothers me when its over-used, though, because then its just distracting. Stephen King, for example, seems too fond of it.
A shining example of the effective use of slang and dialect in narration as well as in dialogue is Mark Twain's Huckleberry Finn (for that matter, pretty much all of Mark Twain's writing does this). Most people don't quite identify the core reason, but writing that is generally described as "folksy" usually handles dialogue in this way. Anthony Burgess' A Clockwork Orange also uses slang in both dialogue and narration, but is a bit harder to wade through until you begin to learn the lingo. The main thing to watch is that you don't make it so thick as to be impenetrable to someone who is not immersed in the portrayed culture or subculture.
I tend to not use much slang in narration, and when I do, it's always very minor (more informal than slang), in direct reference to the thoughts/reactions of that particular POV character, and almost always used in a sort of humorous way, like an exaggeration of how the character is thinking/feeling. I think this is because like I just said in another post around here, I like to keep a certain distance between myself (the uninvolved narrator) and my characters; if the narrative voice (in third person) uses too much slang, it's getting too far into the character's head and making it nearly first person, which I don't want to do. But that's just me. The other suggestions here are good. Primarily, be aware that the slang you use will probably become quickly dated, which is okay if the story is set in a particular time frame, but not okay if you're just trying to be "hip" (a slang word I think is outdated!) or if you use a lot of terms other people won't get. I have never, for example, heard of the term "swisha" because I don't listen to rap. *shrug* I wasn't aware "packing heat" was outdated. Kind of cheesy, and old, yes, but not outdated. :/ I wouldn't see anything wrong with the character using that phrase for humorous effect, or if they themselves aren't quite up to speed on current slang. I know I'm not! ETA: I assumed the original post was about slang/informal language in third-person narration, not first person, so my comments apply mainly to that. IMO more slang is acceptable in first person but the same disclaimers as above apply.
