Use the following search tools and the help pages of databases and catalogs for many more useful tips
For example searching for "marketing and teens" will bring up records containing both those words, actually reducing the number of hits.
Doing a search for "elderly or aged" will reveal records using either term, thus broadening the search.
The final Boolean word, not, is used to exclude terms as in "children not adolescents".
If you want to broaden your search even further try using truncation to bring up variants of a word. For example entering comput* in Academic Search Complete databases will search for computers, computing, computerized, and so on.
Different databases or catalogs may use different symbols, so look at the help page to see which to use.
In a database look for a list of subject headings, index, or a thesaurus to learn how the articles within a database will be organized.