THINK first, SEARCH later.
Always remember: KEYWORDS are critical!
Here's an example.
My topic is "Females have brought a positive element to the military."
My keywords in this topic are "female" and "military" and maybe something like "benefit".
My "related words" lists might look like this:
So I could mix and match - pick one word from each list and I could get great results from each search!
OR - if I wanted to be even more specific, I could make a phrase: <"Female soldier"> and then add a word from my third list: <benefit>. My full search would look like this: <"female soldier" benefit>
See how that works?
The following links provide additional resources for developing a research strategy. Use the strategy that works best for you!
One thing to keep in mind when you are doing research on your topic is that there is NO SUCH THING as a single perfect source that you will be able to cite to support your thesis. Researching and writing is a process of learning about your topic, thinking critically about what you've learned, and supporting your thesis through referencing a variety of sources.