This article is going to take you through setting up BuddyPress for the first time. It is geared towards people trying to set up Social Networking sites with features similar to those available with Ning or other hosted Social Network providers, as such it assumes that you will want all of the features of BuddyPress, plus a few more (well, a whole bunch more!).
BuddyPress Members Only is a BuddyPress plugin that will redirect any attempt to access your sites pages from none logged in users to the register page thus enforcing a completely private network.
LH Private BuddyPress is a simple, single mission plugin with no settings to change, you install and activate it and it immediately turns your BuddyPress site into a private network in so much as once it is active then any attempt by a non logged in user to access any of the BuddyPress pages will be redirected to the login page.
BP Registration Options is a simple plugin designed to do two things: It enables moderation of new BuddyPress users, and it turns a BuddyPress site into a private network.
BP Simple Private is a Plugin that allows site admins to create fully private networks within their BuddyPress site.