Let's start with the basics - identifying keywords in your topic sentence.
My topic is "Females have brought a positive element to the military."
My keywords in this topic are WOMEN and MILITARY and POSITIVE.
I want to find information about women in the military, not in any other occupation. So that needs to be a keyword. If I don't include MILITARY as a keyword, then I could get articles about women in education, or physics, or anything!
I'm not looking for information on men in military, so I also need to make sure WOMEN is a keyword.
Finally, I want to find articles that discuss the POSITIVE aspects of women in the military. If I don't include POSITIVE as a keyword, I might get articles that talk about roles of women in the military, or challenges, or other issues.
Why didn't I use ELEMENT or BROUGHT? Think about this: Are those words as important as the others? Can you rephrase your topic sentence without using them and still have the same topic? They don't convey a specific concept the way the others do... they merely support it. So try to avoid supporting words and focus on the keywords - the really important concepts that are critical to your topic.
PRO TIP 1
When you start breaking down your topic sentence, think about the words that absolutely cannot be omitted, or Galileo will go searching down the wrong trail!