Choose a topic
If you have the option, choose a topic that you find inherently interesting. Should the topics be assigned, attempt to focus on a facet of that broader subject that piques your interest. It may be necessary to read a bit before settling on an initial topic.
Engage in some preliminary reading. An initial web search is passable. Books and encyclopedias, even Wikipedia, can be good at this initial stage. Look at how the book or wiki breaks the topic down into sections or chapters.
Particularly, if you are not familiar with the details of the topic, broad generalized sources like reference sources, fact sheets, and overviews are a good starting point.
Start keeping track of the basics: who, what, when, where.
If you begin with a broad Google search, be critical of the sites you use. Try limiting your search to specific domains (.gov, .mil, .edu, .org). There is, of course, no absolute guarantee of veracity, but these sites tend to be more authoritative. You can force the domain by adding site:mil, site:gov, site:org, site:edu after your search terms.
This is the time to think broadly and consider alternatives before settling on a final research question. Consider what you have learned through this initial information gathering phase and ask yourself: