See the Search Tips handout (pdf) for more information.
Remember: You can use * to truncate, and "quotes" for exact phrase searching; see below for examples.
When searching, group synonymous or similar terms using OR, then combine with other grouped terms using AND.
Searches should be constructed like this:
(termA1 OR termA2 ...) AND (termB1 OR termB2 ...) etc.
If my search topic is, "What are the effects of the armed conflict in Afghanistan on pregnant women and mothers?," I might try a search like this:
(war OR warfare OR "armed conflict") AND (mothers OR maternal OR pregnan*) AND afghanistan
See also this Literature Review Workflow, which lists the steps in researching and writing a paper, may help organize your time