This advice is going to be hard to write without putting in some examples that may be seen as offensive by some. I have used # in these words where the vowels should be to keep it a little cleaner without making people have to guess too hard as to what words I'm talking about. I have been very careful to try and use these words in what is genuinely their correct polite context or for the purpose of giving alternative words for the same meaning. Before anyone reports this advice, please have a close look at how I've used these words and why, look them up in a few different dictionaries if you don't believe me, and if you are still not satisfied, message me and recommend how I can edit it to your satisfaction.
Whether the problem is a developed habit, the result of being extremely upset and needing to be more harshly expressive, or a vain attempt to appear "cool" or "tough", we can't protect our children from hearing, and then trying, to use swearing as a part of their everyday language. However, with a little encouragement, education, and three little rules, we can all at least cull the amount of profanity used and the harsh offenciveness in which it is used.
I learned these rules from my mother, and found that a couple of English teachers at my high school and again later in college also used this method, and it works with adults as well as children. It requires that everybody in the household, classroom, or group must learn and abide by these rules equally - which means practising what you preach.
Rule 1.
The swearing person must repeat what they said, over and over again until they can say what they were wanting to say just as effectively, without the swearing. Until they can do that they don't receive any response other than, "What did you say?" or "Please repeat that?". Eventually they become really annoyed at having to say things repeatedly without thinking about them first. They quickly realise that thinking before speaking has a benefit, and they'll be more careful with what they say and to whom. Just making the person appologise for the offence doesn't work, as it becomes a routine of swear, say sorry, swear, say sorry, and it means nothing and teaches nothing. Just make them say it again... and again... and again until they say it appropriately. Be aware that, at first, some kids might think its funny to swear and you make them say it repeatedly, thus they get to swear directly at you repeatedly, but it won't take long to wear off and loose it's appeal. Just keep your composure and become completely stubborn about it, and you will win in the end.
Rule 2.
Allow the use of swearing under very strict conditions, such as when directly quoting what someone else said, or when the swear word is the most appropriate word for the situation and is used in the right context. Insults do not count for appropriate use (see point 3 below). For example, when talking about a female dog, the term b#tch actually means that. For a child born out of wedlock, b#st#rd is the old fashioned correct term. A male fowl (chicken, peacock, etc) can also be properly called a c#ck. This creates an appreciation for these words, where they come from, and what they really mean. You will hardly hear these words used as it's very rarely that these words can be used. After all, how often do we talk about specifically female dogs, the circumstances of children being born out of wedlock, or male fowls? It's like the word 'giraffe'. It's a word everybody knows, but it is certainly not everyday we have reason to use it. You will find that words like f##k will never get used, as copulation or fornication is far more appropriate. Same goes for crude reference to body parts, as the correct anatomical term is more appropriate. Faeces or excrement should be used in preference to sh#t. If we think about it, there's not a lot of use for a lot of swear words.
For those who just can't keep up with the new terms that your kids are now using, to keep it simple, if it's not in the family/classroom/group's dictionary - and proven to be so (Hint: Avoid owning a comprehensive recent edition. Before buying, look for some of the more offensive words in it, if they exist in their offensive slang definition, don't buy it) - and the word is not used according to the correct dictionary definition, the word can be completely forbidden for the sake of not having to spend hours researching the meaning and origin.
Giving this inch allows everyone to feel as if they have some power to use these words, without giving a mile and a licence to swear freely. They will appreciate the little bit of freedom and will be more acceptable to the new rules, and the sneaky part is that their foul language use will be very restricted, and they won't even fully realise it! For general hit my thumb with a hammer type swearing, insist on things like "OUCH!" and "Oops!".
Rule 3.
Swearing is not to be used for a plain old insult. Why call someone a b#tch when you wouldn't bother calling them a dog? It's used only because it's swearing and that makes it more offensive to some people. Encourage your children to use a thesaurus and dictionary. It's especially good if you can get them an older one with more old-fashioned words. Let them learn and use words like gormless, strumpet, insipid, torpid, boorish, obtuse, and vile when they really feel the need to insult someone or something. I don't know about anyone else, but I find it more offensive to be called "a vile obtuse strumpet", than being called the more modern simplistic version, "an ugly stupid wh#re". Also, for Australians, find a good clean Aussie Slang dictionary. Terms like "having a roo loose in the top paddock", being a "Galah", or calling someone a "drongo" is far better and more socially acceptable than the modern swearing equivalents.
Conclusion:
Implimenting these rules makes everyone involved think before they speak. They will swear a lot less, if indeed they swear at all. They will learn an appreciation for the uses of language, expand their vocabulary, and increase their general knowledge. It also empowers them to be able to fully and strongly express themselves in the most appropriate manner in any circumstances.
Other recommendations:
A great reference for understanding how the English language evolved, where words come from, why we speak and write English the way we do, and even the purpose and reasons for swear words and swearing, I recommend reading a book by Bill Bryson titled, "Mother Tongue". I also recommend doing something that may seem a little weird, but it helps a lot, and that is read a dictionary. Start at A, and read each word and its definition. When you find one that strikes your fancy and you'd like to add it to your vocabulary, make a note of it and start using the word whenever the opportunity arises. Have a "word of the month" getting bantered around the house. Your children's mates might find it "cool" when you child starts using their new word of the month and teaching their mates the new words as well.
Also, when writing something that isn't vitally important, every now and then, when you find yourself using a dull word that you have used many times before, pick up a thesaurus and see how you can reword it so that, you are not utilizing a dreary term that you have employed at innumerable opportunities previously. It can make life a fraction more interesting. Just don't do it too often or people might get a little annoyed at having to constantly get out their dictionary to find out what you are on about!
On the contrary:
I've written another advice called Talking A Different Language on how offensive words that are often used in today's social common language have actual inoffensive original meanings. This can be used in coordination with Rule 2 above, but be aware it can make for some strange looks and needs for explaination in polite company. LOL