One of the best resources for conducting keyword research is the AdWords Keyword Planner.
Click "Search for new keyword and ad group ideas". Then, put in your home page or a competitor's site in the "Your landing page" section. Click "Get Ideas" and Google will return all the keyword ideas it believes are relevant to your site and/or landing page. Download a CSV and sort by "Avg. Monthly Searches" to see what terms have the highest traffic opportunity.
