Put quotation marks around words that you want to stick together as a phrase
Add "site:.gov" to the end of your search to ONLY search websites on government domains
Add "site:website.com" to search only the content of a specific site (for example: charlottesville.org!)
Add "filetype:pdf" to ONLY search for information you think is likely to be in PDF format (reports, documents, etc.)
Use the minus sign or dash to eliminate results that are off target (Example: food system -digestive)
Remember that Google is only a computer, and doesn't understand the concepts in your search. So, try your search using different keywords and phrases that mean the same thing.