One of the most powerful ways to connect with your readers is to "speak their language." However a lot of us find it's hard to strike a balance when it comes to swearing. Sure, it makes sense over cocktails, but in a book? I love this question, and it comes up a lot.
The short answer is, there is no short answer. Whatever you decide it needs to be a conscious choice. Here are some questions that will help you consider.
1. Is swearing an essential part of your brand?
We all know writers, comedians and even motivational speakers who've made swearing a major part of their brand. It makes them more authentic because it's a natural part of their voice. "Adult language" doesn't sound so offensive in a context where people have come to expect it.
However, if you're doing this, remember that your use of that language will help define your audience. In essence, it helps you niche to a give no *ducks* audience, who don't those words without a second thought. They prefer that style, because they consider it more real. Other people, who prefer to get to know a gal better before she starts swearing at them, will be turned off. You're drawing a line in the sand and choosing your section of the market, So make sure you're conscious of the choice you're making.
For instance, I don't swear in this blog because I think it would be distracting. I usually have a specific message about spirituality, creativity, or writing that I'm trying to get across, and in those cases swearing would detract more than it would serve. So I don't. It's a conscious choice I made when I started to define my brand.
On the other hand, in my fiction, I'll drop an occasional F-bomb for either emphasis or humor, but in those cases it's very carefully placed. In those cases it adds more than it detracts. Which brings us to the next consideration...
2. What's the purpose?
If swearing isn't a part a regular part of your repertoire, you have to realize that if you do use adult language now and then, it's going to draw attention to itself. Just try to notice this in your own reading, when you come across a swear word, does it affect you more or less than in regular conversation?
Often adult language stands out more text. It draws attention to itself. This can be used as a tool, but it's important to know what you're doing. Make sure you're using those four letter words in climactic places where you really want to draw attention. This is actually how I use swearing in fiction, sparingly and with very conscious placement.
3. Does it sound better without it?
At the end of the day, do an edit. Replace the swear with something less loaded and see if it sounds silly. The fact is that even if you avoid swearing as a general rule, sometimes that bad word is the one you have to use. Write out both sentences (with and without) and compare them.
Using the controversial word might be funnier, but sometimes it's taking the easy way out. If you can stretch your imagination and find more than one way to get the same result you're always going to grow in your craft as a writer.
As you practice and become more conscious of the way you use words, you'll start to come up with your own style guide. Like a magazine. This is a great way to find your voice and establish your identity as a writer. With time you'll build confidence, take new risks, and really enjoy the process.