Quotations marks (" ") will group words as a phrase, ensuring they appear next to each other in the record. For example:
will return only articles that use those terms right next to each other.
whereas will return articles that may mention Great in one part of the record and Depression in another part of the record.
An Asterisk (*) at the end of a term will allow you to search for different forms of a word with what you enter as a base. For example:
will return Education, Educator, Educators, Educate, Educated
will return just Education exactly as you type it in.
This is a very simple and effective way of broadening the number of results you get.