I just finished taking a full day course at the Ottawa County mental building which prepares a person to understand the different kinds of mental health problems that people can have and what kinds of interventions are usually required.
Some of the topics covered are depression, anxiety disorders, psychosis, substance abuse, and eating disorders. The course helps you to understand these people better and trains you to encourage them to use both self help and professional help. It also points out when public safety officers need to be called. A test is given at the end of the day to be sure that you have picked up all the basic ideas.
You also get a good 125 page textbook to take home that has even more information in it, including web sites and a list of references for further reading.
This is a good investment if you have to deal with the public often.