Avoid terms that don't have important meaning in terms of a search.
Think to yourself whether a word will add meaning or not. Suggestions of
word types to avoid: adjectives, adverbs, articles (a, an, the),
prepositions (in, out, with, for, from, etc.), and even many verbs.
Don't be afraid to be detailed in your searching while using web search
engines - they're pretty big and will likely find something. In the
above example, the searches go from less to more specific. If you're not
getting many results, broaden your search a bit.
Another way to be specific is to use phrase searching when you want
two or more words to appear in a precise order. Most search engines
allow this by placing " " around a phrase. Ex:
"Much Ado About Nothing"
Some search engines will allow you to enter multiple terms for the
same concept (search engines may differ on how or if they allow this).
Think about synonyms and plurals. Examples:
Cat: cats, feline, felines
United Kingdom: Britain, England, Scotland, Wales, Northern Ireland
Use the search engine's advanced search
If a search engine has an advanced search, it will open up many
opportunities for you, including:
Specifying format, language, domain, years, etc. Multiple search
boxes for all terms, any terms, and exact phrase
(some have a box for terms to exclude)