Add site:edu or site:gov to limit your search to .edu or .gov sites
Limiting your search to the areas of the web where the information is most reliable, such as education sites or government sites is a good way to find credible sources.
For example, a search for nutritional supplements, will bring up many commercial (.com) sites trying to sell you vitamins. If you search for nutritional supplements site:gov , the top results (except for the sponsored ads) will be sites such as the National Institute of Health and the Food and Drug Administration, which are authoritative, unbiased sources that are not trying to sell you anything.
If you search for nutritional supplements site:edu, your top results will be from universities providing research on nutritional supplements.
Use a minus sign to exclude words.
For example, if you are looking for weather information in Portland, Maine you could add -oregon to your search to exclude web sites with the word "oregon."
Or to exclude commercial web sites, add -site:com to your search. For example, nutritional supplements -site:com
Use "quotation marks" around phrases.