Keep track of your search and your results. Remember research is a process and you may try many things before you find what works best for your topic.
Keep track of your search terms and write down other words you find while perusing the articles that result from your searches.
The "search history" option under the search box can also help with that.
Email, print, or save articles that might be useful for your research, even if you're not sure that you're going to use them.
If your topic is:
Does mental health stigma deter college students from seeking treatment?
1) Identify keywords or phrases:
mental health stigma college students treatment
2) Explore synonyms for your keywords/phrases:
Mental health: well being, psychological health, mental illness, depression, anxiety, stress
Stigma: attitudes, perceptions, values, stereotypes
College students: university students, undergraduates, freshmen, higher education
Treatment: counseling, intervention, therapy
3) Use these terms in your search. Combine the synonyms with the word "or".
For example: mental health OR mental illness OR psychological health OR depression
Reading these sections of an article/book will help you determine if the item you're looking at is relevant to your research.