Although you may be limited by specific classroom or work related guidelines, choosing your topic is the first and most important step in your research paper project. Regardless of whether your topic can be anything you want or has rigid requirements, it is important to keep a few questions in mind: Is there enough research available on this topic? Is the topic new and unique enough that I can offer fresh opinions? Is it pertinent to my class/occupation?
If you find one really awesome book or journal that fits your topic perfectly, try looking in the works cited/bibliography/reference list at the end of it. This should contain many more books and journals that are about your topic as well.
An argumentative research paper takes a position on a contentious issue and argues for one point of view. The issue should be debatable with a logical counter argument.
Any information that doesn’t fit within the framework of your outline, and doesn’t directly support your thesis statement, no matter how interesting, doesn’t belong in your research paper. Keep your focus narrow and avoid the kitchen sink approach. (You know, the one where you throw in every bit of interesting research you uncovered, including the fungal growth in the U-joint of your kitchen sink?) Everything you learn may be fascinating, but not all of it is going to be relevant to your paper.