Truncation and Wildcards
You can use truncation and wildcards in many databases, catalogs, and search engines. Each database may have its own truncation or wildcard symbols, but the following are common:
Google has its own fantastic set of symbols. To construct a really good advanced search in Google, see the Google Search Basics page. (I'm a big fan of Google's version of the wildcard. In Google, the asterisk can stand in for an entire word. Google's example: Obama voted * on the * bill.)
Note: You can use OR in Google. You just have to capitalize it.
Often, you'll discover the right level of focus as you begin your research. Encyclopedias and dictionaries can be a great place to start this research. Use these resources to get topic ideas or for background information.