Your first decision is whether you want TagPiG to run in fully automatic mode.
Most users will, so leave the Auto Tag All New Posts box ticked. This ensures that every new post that is published (either manualy or via the WordPress scheduler) is automatically tagged by TagPiG.
If you uncheck this box then TagPiG wil stil work but you will need to click the add tags now button inside the new posts screen in WordPress admin. See later section for more information.

You have a choice of 4 sources of tags for your blogs post.
Yahoo – By leveraging Yahoo’s Search API TagPiG is able to extract a list of all significant words or phrases from your blog posts. These can be used as they are or filtered further as needed. We highly recommend checking the Yahoo source check-box.
Open Calais – The Open Calais API provides one of the most comprehensive text analysis engines available today. Not only can it return the main targeted words from you post but also additional phrases or categories that it considers are related to your post’s theme. You will need to use your own Open Calais API key as we are not allowed to share our key. You can get a free Open Calais API key instantly from here. To get the widest variety of tags keep the social and topics options checked.
Zemanta get API key
Alchemy get API key
Local DB are Tags that are already found in your wordpress site.

Embedded Tags – If you already have tags prepared for your blog posts you can easily import them by putting them inside your post content and enclosing them between [tags] [/tags] shortcodes
e.g: [tags]gadgets, widgets, mobile phones, calculators, Xbox 360[/tags]
TagPiG wil automatical y extract these tags and display them as tags below your post Removed

We have several more tag sources in testing right now, stay tuned for updates.