Please see Using Plugins for an updated version of this tutorial.
Plugins in Quantum GIS add useful features to the software. Plugins are written by QGIS developers as well as other independent users who want to extend the core functionality of the software. These plugins are made available in QGIS for all the users. Here I will show you how to access the official as well as un-official plugin repositories and install these plugins in QGIS.
Open QGIS. Click on Plugins → Fetch Python Plugins Select the ‘Repositories’ Tab and click ‘Add 3rd Party Repositories’. Once the repositories are fetched, you will be in the ‘Plugins’ tab. Type a keyword or the name of the plugin you want to install. Here we are looking for a plugin called ‘Table Manager’. Select the plugin from the list and click ‘Install Plugin’. Once the plugin is successfully installed, it will be added to the Plugins menu. You can manage the installed plugins by going to Plugins → Manage Plugins... Find your plugin and click on the check-box to enable or disable the plugin.