Yes, there is an abundance of information available via Google. Yes, it is an easy tool to use. No, not all information retrieved through the Google website is valid. You already know this. So, how does one use Google the SMART way?
Know your domains: .edu=education, these are college and university websites and are generally very trustworthy; .gov=government, a simple .gov is the federal government, these are always trustworthy; .mil=military, very good for policy papers; .com=commercial, be wary of these; .org=organization, be wary of these, too. They might be fine (trade unions, clubs) but they might have agendas that will skew the facts on their page. .net is now synonymous with .com and should be treated with the same regard.
In any instance, ask yourself, "In whose interest is it that I should believe this material?"