Think about keywords or phrases that are important to your topic:
Example paper topic: women in prison
Example search terms: women, females, inmates, offenders, prison, incarceration, "female prisoners", "female inmates", "incarcerated women"
Also, think about what you want to know about your topic:
Example paper topic: women in prison
Example questions: Why is the number of women in prison increasing? What is the experience of women who are in prison? Why do most women go to prison? How do mothers who are in prison maintain a relationship with their kids? What are the mental health effects of women who are in prison?
Think about how to incorporate your questions into your search terms:
Example paper topic with question: How do mothers in prison maintain a relationship with their kids?
Example search terms: women, mothers, moms, parents, inmates, offenders, prison, relationship, custody, "mothers in prison", "parenting from prison", "incarcerated parents"