You can limit your searches in several ways:
Search within a site or domain - type .edu
Use flexible vocabulary - if one phrase or combination of words doesn't work, perhaps another will.
Limit by Language, etc.
Google Search Tips (MIT Libraries)
BEWARE: Always remember to evaluate the quality of the site you are viewing. Don't believe everything you read unless the information comes from a reputable or reliable source.
See Evaluating Web Pages: Techniques to Apply and Questions to Ask (Univ. of California Berkeley Library) Consider authority, accuracy, objectivity, currency, and completeness as you evaluate whether to utilize the information found on a particular Web page.
Power Tips (Tech Insider) - Video (about 2 minutes)