Take it Apart
When starting a search, many people type in a phrase, such as: arts in the classroom. This may not yield the best results though, since most search engines will start by trying to find the whole phrase.
Instead, take your topic and pull the main ideas out into keywords. A better keyword search might be: arts AND classroom, or, arts AND teaching, or, arts AND pedagogy.
Think Outside the Box
We often start with a single term, like "theater," and all our searches revolve around that term. Searching with synonyms and related concepts will help find results you may have otherwise missed. Searching for: teaching AND (theater OR drama OR acting) will yield far more focused results than a search on just the term 'theater". (Don't forget different spellings too! i.e. "theater" and "theatre.")
Let Other People Do the Work
Unlike a web search, most catalogs and databases are organized with a controlled vocabulary. This means that every resource indexed in it - books, artcles, etc. - have been assigned specific subject terms. These often appear as part of the citation - look for tools that say Subject, or Subject-Thesaurus Term. By clicking on subject terms, you'll immediately be directed to other items that have been classified with similar content. Controlled vocabulary is a very powerful search tool - use it.
Step Up to Advanced
Almost every search engine, catalog, and database offers an Advanced Search feature. Most will allow you to search on multiple terms, sort for full-text, date ranges, and type of publication, as well as remove certain types of results from a search (like reviews or editorials).
AND - use this when ALL the words must be in your results. This will narrow your results. Example: apples AND oranges; peanut butter AND jelly
OR - use this to connect synonyms, when ANY can come back in your results. This will broaden a search. Example: women OR woman OR girl; cat OR kitty OR kitten
NOT - use with caution since this will eliminate results with the specified word.
Key take away: You should always use multiple databases and sources if you want to succeed with any research project.