Getting Information from POST data

I am trying to create a plugin that takes the POST data from an order and emails it to the end user. Which property should I use to do this? I’ve already tried to use getContent() and getContentFromPost().

So for example if I have

         <input type="text" name="dataName" value="">

And in my plugin I’m trying to get the value of “dataName” which property should I use?

$value = craft()->request->getPost('dataName');