I was hoping you would have enlightened us on what sort of topic your question is more directly associated with, but excusing your question's vagueness I'll still try to help.
Foremost, you should understand the problem you are trying to find solutions for. As simple as this sounds, it's commonly overlooked as part of the brainstorming proccess. If I gave you two numbers and asked you to find the solution, you wouldn't know what sort of solution I was looking for if I had yet to point out that I was looking for the sum of both numbers. If you are on the phone with someone who's asking you how to help a choking victim, details on the environment and variables of their situation could be a matter of life and death.
Once we have identified the problem itself, we can then brainstorm on the best way to handle the problem by determining the most efficient variables that apply to the problem we have at our disposal. For instance, getting from point A to point B could be a possible problem. Part of working towards the solution could involve many sorts of variables like our mode of reaching our destination at point B and what resources we have at our disposal to aid us in reaching our solution of reaching our destination. As per our example, and considering the situation, point B could be better reached by a boat, by a ladder, or by specific points on a line graph. Point B could be on the other side of a river with no crossing for miles. Or, point B could be the frisbee that was accidentally tossed onto the roof of a three-story home. Or point B could be the solution to a complex geometry problem. In each instance, different variables can be used for different situations, and the brainstorming can help us determine which way our goal can be better achieved.
I hope this answers your question!