Even better, how to know what word people use to find your competition's website.
Alexa.com is a company owned by Amazon.com that offers remarkable data about your website and your competitors. To see the top performing keyword terms for a website go to Alexa.com/siteinfo and plug in the URL of the website you're researching. Towards the bottom of the page Alexa lists the keywords most commonly used to find the website. On the left side of the page Alexa also shows the sites which refer the most traffic to that website.