If you want to sound serious, and by serious I mean like an adult, the modern writer could very well sprinkle their writing with some earthy prose, like the word fuck.
Did he just say fuck?
I believe he did.
I got to go to the bathroom.
Oh, second door to the left.
Now the quoted text above (self reference if you must know) was an attempt at sounding adult, clever and funny, all at the same time.
I should have thrown in a NSFW warning there.
But most of the time it’s not necessary to swear. Not that you have to have your characters act the proverbial Ned Flanders, fraking every other swear word because you don’t want to offend. If the character wants you to fuck off he should say so.
On the other hand like the proverbial sex scene (again with the not so clever self references, bravo), drop one to many f-bombs and it gets boring really fast, like a South Park episode without the bleeping. In fact I preferred South Park WITH the bleeping, made that much funnier when I had to guess what those little bastards were mouthing off in every other breath.
There are always exceptions to the rule.
(Exercise extreme caution in pressing the link. Lots of naughty things will come streaming through your speakers. Just saying.)
But again, your mileage, well you know.
It really comes down to word choice. Sometimes a good fuck goes a long way. Sometimes not, then again it should always go a long way, unless it was a bad fuck, in which case, well shit, your fucked!
Remember it is only gratuitous if it doesn’t work.
Now please, get your bucket of soap, a comfy couch and enjoy the following short film: