Select the most important 2-3 ideas related to your topic. Put the word AND between each new word or idea; this tells the database to look for resources with ALL your terms.
obesity AND children AND schools
Use quotation marks ( " " ) around phrases (two or more words); this tells the database to look for the words in a specific way.
"junk food" AND obesity AND schools
Use the asterisk (*) to truncate a word; this tells the database to look for all words that have the same base. In the example below, search results would include "risk," "risks," "risky," and "risked."
"coronary artery disease" AND angioplasty AND risk*