It depends on your intended audience. For my money, I wouldn't put curses in just for the sake of being edgy or mature, but if it seems absolutely natural for a character to use them then I'd prefer to see them in. And avoiding them can seem unnatural, though that may depend on the individual character, some might conscientiously avoid swearing while another might swear like a sailor.
Depending on the setting (such as fantasy or science fiction unattached to our world) you might use invented curses. Though this can also seem forced or unnatural, depending on how well you do it.
There's one interesting solution I saw in the sitcom Father Ted, which allowed a great deal of foul language before the water shed by taking advantage of the character's Irish accents. "Feck."
Well, it depends on what sort of comic you're making: if it's the sort of gritty, realistic story then yes, swearing will be part of it because it happens. If it is comedy or something light and fluffy you can still have the F bomb but kinda censor it very obviously so it gets double comedic effect. If it is for kids, no. If it is for teens go ahead, they have more imaginative cusswords anyway! aaand if it is fantasy or scifi you can invent your own frak-word.
Again you might have heard of this, but it depends on what your story is. The setting the mood and the characters will define your story, so if its about lets say a young latina girl with a back pack with her monkey friend who wears boots then cussing would be a no. If its about a group of sailors on shore leave in a third world country trying to have their way with the local women, well you know where I'm getting at right?
If you are paying, Curse. If you are getting paid, Sit and pant at any order. Personally i try to write without swearing... but sometimes the story gets better with people swearing like kindergartners around an alcoholic father.
I think that if your story matter is already adult, then swearing is fine... like if you have any nudity or suggestive talk etc, then not adding in swear words might seem weird. I think you should just define your audience you are aiming at before asking this question. Is it young adult? Some not-so-harsh swearing is fine. Is it young adult + kids? No swearing. 18+? Swearing.
This question depends entirely on the tone of the work and the intended audience. If it's meant to be a very light-hearted work, or intended for children or "all ages," you should omit curse words. In any other circumstances, however, you should use them. In the real world, people swear when they feel it is appropriate. Most stories I know of involve people in rather trying situations, and in that case it may be more jarring for them to not swear. Not to mention that what people consider to be "appropriate" cause to swear is highly variable, and can tell your readers something about there character. A person who never swears, regardless of the circumstances (or, heaven forbid, uses only minor oaths like "Gosh darnit to heck!) is probably going to be some sort of stuck-up, austere, overtly-moral character (a preacher, perhaps). On the other hand, a person who swears frequently shows a lack of discipline and concern for their outward appearance (like a thug, or a common laborer). Beware of the latter case, though. Verisimilitude can actually come off as distasteful, when it comes to swear words. In the real world, I know a few good-for-nothings who use "fucking" like a discourse particle: "It's like, you know, fucking..." Usage to that extent is grating on the nerves.