Google Analytics provides rich data about user activities on your Web site/landing page that can help you optimize your keywords. The following are some of the techniques that you can leverage.
The Organic report in Google Analytics provide a list of organic keywords and their respective performance. These are the keywords used by people to land on your Web site and they can provide good insight for optimizing your paid keyword list. As indicated before, there is no reason to invent new keywords; you can learn from organic keywords. Consider the following example: