Facebook is probably the most popular fully featured social network depending on your definition. Is is media rich with videos and photos and discussion. Friends must agree to be friends.
Start with a personal account, then tie down your privacy settings under "account" top right. You don't really want all your customers seeing your personal family and friends photos and dialogues.
You can then create a "facebook business page" for your business focus. Your customers can become fans of your business page, while keeping your personal account private.
Add tabs to the top of your business page, and you can search for special applications like "polls". Add your events, add your links, add your news bulletins, but start by asking some questions, and engaging your members/customers/fans to participate. They might be timid at first, but if you can encourage a few over a glass of wine, then you can start the ball rolling. Once there is some active discussion, be sure that more will join in.
Remember that the most important thing you can do, is get other people to post on your wall, to comment on your posts, to "like" things. So try not to tie down the settings. Try and open it up, release your control and your worries. You can always delete anything later, but the great thing about facebook is all usage is by verifyied users, so you tend not to get any spam on your pages.