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.
The introduction is, in many respects, the conclusion written in reverse: start by generally introducing the larger topic, then orient the reader in the area you’ve focused on, and finally, supply the thesis statement. Avoid repeating exact phrases that you already used in the conclusion.
Now that you have carefully worked through your evidence, write a conclusion that briefly summarizes your findings for the reader and provides a sense of closure. Start by briefly restating the thesis statement, then remind the reader of the points you covered over the course of the paper. Slowly zoom out of the topic as you write, ending on a broad note by emphasizing the larger implication of your findings.
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.