A single main point doesn’t have to be kept to a single paragraph, especially if you are writing a relatively long research paper. Main ideas can be spread out over as many paragraphs as you deem necessary.
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.
All research essays must be documented in certain ways in order to avoid plagiarism. Depending on the topic of your research and your field of study, you will have to use different styles of formatting. MLA, APA, and Chicago are the three most common citation formats and determine the way in-text citations or footnotes should be used, as well as the order of information in your paper.
Although it may seem counter-intuitive, writing your introduction first may be more difficult to accomplish than starting with the meat of your paper. Starting by writing the main points (focusing on supporting your thesis) allows you to slightly change and manipulate your ideas and commentary.