Advice: Online dating
This assumes that you want to meet someone in real life as opposed to having a cyber relationship.
When advertising be honest in saying what you are looking for. If at all possible post a picture of yourself, it dramatically improves your chances of someone responding to your advert. The chances of someone at work stumbling across it by accident are about the same as winning the lottery (and if they are looking at it, chances are they have the same sort of interests as you). If you are looking for a long term relationship then clearly state that you are "not interested in married men or similar".
When answering adverts don't just talk about the kinky sex! A mutual interest in fetish and BDSM might be what has brought you together but a relationship requires more than that. Try to tell the person something about yourself, if you are a man responding to a womans advert then the chances are that there are a lot of other people emailing her too. Check your spelling and grammar, you want the person receiving the email to read about you, not pick holes in your composition.
Although some people feel that they want to get to know someone via the Internet quite well before meeting, experience often shows that it is best to meet up as quickly as possible. Corresponding by email is not the same as meeting someone in the flesh. The problem with emails is that it is all too easy to construct a mental image of the person which has no relevance to what they are like in real life. Then when you do eventually meet them you will be disappointed to find out that they are not the same as your mental image! You will also avoid the disappointment of building up a relationship with someone who for all their good points does nothing for you physically.
Follow your instincts, if after dating someone for a while they still don't want to invite you back to their home or meet their friends then it is likely that they are married or in a long term relationship. It is a sad fact of life that a lot of people (especially men) try to use dating sites to cheat on their partners.
99% of people are normal sane individuals, that does not mean that you should not take steps to ensure your own safety when meeting someone for the first time.