Use "AND" to narrow your search (usually by combining terms representing different concepts).

Use "OR" to broaden your search (usually by combining synonyms or terms related to the same concept).  

EXAMPLE:
What are effective methods for teaching reading to students with ADHD?

(attention deficit disorders OR attention deficit hyperactivity disorder OR ADHD)
AND
(teaching methods OR classroom techniques)
AND
reading instruction

1. Use truncation or stemming to find words with varying endings:
theat* finds theater, theatre and theatrical

Characters used vary by database; the most common are *, #, !, or ?. Look for "Help" to find which character to use.

2. Use wildcards to find words that vary by a single letter:
wom?n finds both woman and women

Look for "Help" to find which character to use.