What are you trying to determine for your literature review? What specifically are you trying to learn more about? Essentially, what question are you trying to have answered?
Choose your topic of interest and start by conducting a broad search on it. Determine what kind of trending and popular research has already been done on your topic.
Narrow your topic down in a way that is relevant to you. You can refine your topic by one or more of the following:
Having more specific research terms will help in defining your question.
A broad question might be something like:
What is the homeless population like?
A more narrow and specific question may include:
What social and political factors have affected the growth of the middle aged homeless population in Toronto within the past five years?
Once you have determined an appropriate research question/topic, then you can move on to planning your approach.