Another technique that can improve your search results is called truncation. Truncating a word means that you are able to search different forms of the same word at the same time. It's great for returning results with alternate spellings, and results that begin with the same root word.
Truncation requires the use of symbols, called wildcards, to replace word endings. The most common symbols are: * ? #
Different databases use different symbols. Check the database's help menu to find out what the standard symbol is for the database you're using.