1] Ability to limit user sign-up to specific email domains, if required
2] Allows common administration panel for all user sites to restriction or control of User Choices (Roles/ Activities/ Themes/ Plugins, Security Precautions and Protections, Spam protection, etc)
3] Options that include usersite’s personalized user administration features for adding Plugins/ Themes
Before the release of version 3.5 (V3.5) of WordPress, this feature was available as a WPMU Plugin. However, with WordPress V3.5 release, it has been incorporate to the core. It can be enabled in WordPress V3.5 by creating a Network, using the WordPress Network tool following the described step in the Documentation.
After deciding whether you need a multisite or a WordPress network, check whether your server meets the requirements. The requirements range from Administration requirements to server Domain requirements.
1] Admin Requirements include access to the host server or should have the Administrator access to create files and directory.
2] Types of WordPress Multisite Network: You can choose from the following two types (domain/ path based), depending on how you want your network to handle URLs, and on whether it will allow end users to create new sites on demand. Different types of network have different server requirements.
2.1] Domain: Sub-Domain installs (installs to the same directory where WordPress is installed) which uses URLs like example1.com, example2.com, site1.example.com, site2.example.com.
2.2] Path: Sub-Folder installs which uses URLs like example.com/site1, example.com/site2.
Note: You cannot create a network for sub-domain if URL is or contains path, or localhost or IP address is 127.0.0.1, or uses port other than 80 or 443. You cannot create a network for sub-directory if existing network has been set up for more than a month. There are methods to force install multisite in localhost for WordPress, however.
Multisite Network Creation
Once the requirements are ready; setup the Multisite for WordPress. Enable ‘Multisite’ option in wp-config.php. Then create and enable the Network using Network Setup (Tools section of Administration Panel), which will guide you through the setup method (with suggestions for appropriate scripts in wp-config.php and .htaccess). Log-in again after a cookie and cache clearing. You should be able to see different sites (Administration Panel > MySites), which can be individually managed. Check for Apache/ WordPress (wp-config.php/ .htaccess) settings and requirements for creating network; in case there are issues with installation. There are automatic installation stacks for WordPress multiuser sites available in the web that helps easy installation and setup.
WordPress MultiUser: http://codex.wordpress.org/WordPress_MU
WordPress – Before you create a Network: http://codex.wordpress.org/Before_You_Create_A_Network
WordPress – Create a Network: http://codex.wordpress.org/Create_A_Network
WordPress Multisite Network Administration: http://codex.wordpress.org/Multisite_Network_Administration
WordPress Multisite Debugging: http://codex.wordpress.org/Debugging_a_WordPress_Network
WordPress Multisite Support Forum: http://wordpress.org/support/forum/multisite/page/3
WordPress Multisite Automated Installers: http://codex.wordpress.org/User:Beltranrubo/BitNami_Multisite