You do not need to be a health professional to start one, either. You also don't necessarily have to have a lot of extra time or money on your hands in order to make a significant contribution to your community. You also need to be willing to give of yourself, both physically and psychologically. Choose a central location for your initial organizational meeting. Hospitals and churches are ideal because their meeting rooms and auditoriums are usually free.
Hospitals also have the added advantage of having better access to possible speakers.
Post notices of the meetings in interested physician's offices, do public service announcements on the radio and TV, and send announcements in to your newspaper's health section. You should also use this meeting to decide how often you will meet, and to set guidelines as to phone calls to the leader and other members for discussions, etc. If it will be a large group, you might want to set up a buddy system where willing participants include their names and phone numbers on a list to be circulated at the meetings. The content of your meetings is up to you and your group's members. You can alternate between having guest speakers and simply having group discussions, or you can choose to only have one or the other.