So, here's the thing - I'm not a fan of casual swearing. I know that might be a surprise coming from someone who has an interview series on her blog called the SHIT. And trust me, RC Lewis will tell you I'm not averse to dropping the f bomb when necessary, so please no one read this and think, "Oh no, I used a four letter word in an email to her one time, she thinks I'm an idiot."
Trust me, I don't. I know some idiots, and you're probably not one of them.
What I dislike is casual swearing, dialogue laced with four letter words contrived to display the character's laissez-faire attitude towards the status quo, the villian's familiarity with gutter tongue, or the inherent toughness of your MC. Here's what you're really doing: Showing that you as a writer have to rely on an over-used group of four letter words to convey intensity.
How to be intense without swearing? I advise watching Breaking Bad in it's entirety, but for a quick example, this clip from Season 3 will do: