1. Don't talk with anyone about the client - When I was a child I remember my mother questioning my father about someone who she saw in his office. He was a Credit Union Manager who was very good at keeping the confidence of others. When mom told him that she knew a person was in his office he merely replied "Is that right?" His theory was that if he didn't say anything about business to others, they wouldn't be able to pass that information along. You see, when you tell someone something, you lose control of that information and, even if the other person promises not to tell others, you do not have any guarantee about that.
2. Make sure that your office is sound-proof - My friend was in the waiting room of a surgeon and heard the staff calling the homes of patients to inform them of the results of the post-vasectomy sperm count tests. She was shocked that names were openly used and that everyone in earshot could hear about this privacy issue. When someone comes to you in order to deal with personal issues, it is important that the two of you will not be overhead by anyone.
3. Keep all paperwork out of sight - Even leaving a client file on a counter or desk opens up the possibility that someone will read the label. It is up to you to have paperwork under lock and key for storage and out of viewing range for cases you are working on.
4. Use wise technology practices - Confidential information should be sent by FAX or under password protection on the internet. Be very careful about hitting "Forward" or "Reply" to emails as your message may go to the wrong person. I always check an address or FAX number before hitting "Send" to ensure that I have entered everything correctly. Also, be cautious that clients are reading over your shoulder as you are scheduling their next appointment!
5. Use good boundaries - If a client indicates that they know you have seen someone else, do not agree or confirm this. I always say "Because of confidentiality, I cannot talk about that. You wouldn't want me to let others know that you have been a client if they ask me, would you?" That usually ends the conversation and re-assures the new client that you will protect them.