"trail of tears"
This ensures that the database will return results that include the entire phrase
"trail of tears"
rather than records that contain both of these words, but not your search phrase:
records that include the word trail and the word of and the word tears but not the phrase "trail of tears"
Doing this will help you avoid sifting through irrelevant results.
afr* will search for
Afro-, Africa, and Africans
The database searches for any word that begins with the letters that precede the truncation symbol (in this case, an asterisk). Some databases use other symbols, such as a question mark, for truncation.
ex. women OR female
migration NOT birds
See the box on Boolean Logic for more about this search technique.