Within Google Analytics it is a good idea to set goal pages for your website. If the goal of your website is to make someone contact you via your contact form make sure once a visitor has filled in the contact form it takes them to a "thank-you" page. Within analytics you then should make this "thank you" page a goal.The same principles apply to a e-commerce site, set the goal as being the "thank-you for purchasing page".
Once you have these goals you are more likely to find out how successful your website is. Each goal visited is then a conversion, with this additional information you can identify the sources that convert the most; the most profitable keywords; the most profitable landing page, and much more to enable to make the most out of your website. As the end goal should be a "profitable website".
It goes without saying that these goals are not exact indications of your website’s success. Google may be a super power, but at present it can not track down the number of people that have contacted you via telephone after visiting your website. That you need to do yourself.