Use quotation marks to search for a phrase (two words or more).
Use AND to join dissimilar terms. It helps narrow your search.
"college students" AND stress
Use OR to join similar terms. It helps broaden your search.
“college students” OR undergraduates
Use AND and OR together, too.
“college students” OR undergraduates
AND stress
Use a truncation symbol (the asterisk * is the most common) to look for different word endings.
You do have to be careful with truncation. Sometimes you might get unexpected results.