Out in the real world, a lot of us swear.
Maybe it’s only in the context of our cars, or whenever our computer acts up. Maybe it’s a way we put emphasis on particularly stirring thoughts. We bleep those words when we say them on TV or on the radio, but I’d be surprised if we didn’t encounter those words daily, either coming from our own mouths or somebody else’s.
But should our character’s swear?
I could give you the whole writer’s spiel on how no words are inherently bad, only the connotation we assign to them. I could say that some people consider swearing in writing to be lazy, whereas others think it is a more natural portrayal of the world we actually live in.
Here’s my take for whatever it’s worth.
I think some words are charged with meaning, maybe not for everybody, but definitely for some. I think if you swear on the first page of your story, you’re likely to swear on most of the other pages, and readers pick up on this. I think some words that are not technically swears but feel that way can also make other people uncomfortable (like feminine hygiene products or the bag they came in).
I’m not say swearing is lazy writing, but I think you should be using it for more of a reason than just “this is how people really talk”. I tend to think sparingly is better than as punctuation, the latter removing a lot of the meaning and power from the word, whereas the former really grabs the reader’s attention at a critical moment. If it makes sense for your particular character, and you are making that choice deliberately, fine. But maybe only have that be one character in your story and not all of them.
As a writer you want to appeal to the widest possible audience, or at least be aware of what affect the choices you make will have on the size of your potential audience. I’m not advocating for anemic writing, something bloodless that offends no one. But you need to be making the choices of who you offend and who you build up deliberately, and not just out of hand.
But what the f— do I know? What do you guys think?
[BTW] : Ben Trube, Writer 
I should probably just recommend Writing Dialogue for Scripts and leave it at that, but to put it in my own words, it’s about writing dialogue that gets across a character, but wouldn’t necessarily be what the character would say ‘in person’. Just like you can remove many ‘um’s, ‘er’s and ‘like’s from normal speech and make it an approximation of speech that’s a lot more palatable to read, you can probably trim swearing if you’re worried about how people would perceive it, or if it would be too distracting.
That said, I don’t often swear, so I might just be making all my characters too polite…
“As a writer you want to appeal to the widest possible audience, or at least be aware of what affect the choices you make will have on the size of your potential audience.”
I actually disagree with this. As a writer, you want to tell your story in the most authentic way possible.
I don’t have a lot of swearing in my writing — well, you’re reading my ms, you know that — but I use it uncompromisingly when it suits the character and the situation. Some characters have their own version of swearing (Vlad’s teeth!), some characters wouldn’t use profanity if they were set on fire, and soe characters will sprinkle profanity lightly through their speech every time they’re angry.
One of the most interesting comments I read about using profanity of any kind of writing was from a female writer who said that she didn’t care how many f-bombs or c-bombs or any other swear word was there. But the moment a character said, “Oh my God!”…. well, that was blasphemy, and she would immediately stop reading and write a negative review of the book.
All of which taught me that you can’t please everyone when it comes to language, so you may as well do the most important thing of all, and please yourself and your story.
I think in terms of dialogue, it obviously depends on the situation. If your character is driving and their car is about to crash, the most common human reaction is “Oh, sh…” Same with f-bombs – if the scene is heated and the characters are flustered, then sure. Personally, I would never use the c-word in anything, ever – but it holds different meaning here in America than it does in other countries. I guess it all depends on your target audience.