To begin to search successfully you must use a variety of words that relate to your topic
This example shown in the image below is drawn from the opening paragraph of a reference article titled "Plastics" that from the encyclopedia titled "Achieving Sustainability: Visions, Principles, and Practices" The image points to stakeholders (Who), facts (What), issues (Why), and where the article addresses what's being done or proposed solutions (How).
State your research question or topic
Extract the main concepts
Brainstorm search words
(click on image to enlarge)
The starting keywords in the broad research question: How do cigarettes impact children's health? are: cigarettes AND children AND health
I would add a column with words for other things I want to know, such as laws, education, prevention, history, etc.
Use the "Advanced Search" to give you more control when you search.
Try different keywords from your keyword list to address the same concept:
(click on image to enlarge)
(click on image to enlarge)