Choose a topic - even if you're assigned to write a research paper, it will go smoother if you are genuinely interested in your topic so choose something you want to know about within the parameters that the teacher has given you.
Do some preliminary research - start with a general encyclopedia or an online encyclopedia (e.g. Wikipedia). You won't use these as sources within your paper but you'll get an understanding of your topic.
Consider your audience - formal research papers require a formal tone (i.e. it's graded by your instructor) but many research assignments ask for students to convey the information in different ways so keep in mind who will read your work and in what format it will be delivered.
Start asking questions - "how" and "why" questions are open-ended and lend themselves to providing the answer in a detailed manner.
Evaluate your question - is it clear? Is it focused? Is it specific enough to be answered in the required length but not too specific? Is it complex? By answering it, the writer should be able to provide some analysis of what the research has revealed.
List what you already know.
List questions that interest you.
Narrow your list of questions. Narrow down your list of questions to topics that aren't too narrow or general, depending on the length requirement of your paper. You won't be able to find enough information on a question that is too specific. A very broad topic will yield way too much information to work with.
Refine your question. Refine your research question to give it a clear, direct focus based on your preliminary research. For example, "How did the U.S. get involved in the Vietnam War?" is better than "What role did the U.S. play in the Vietnam War?" because it is focused on a specific part of a very broad issue. You'll have an easier time writing your paper if your research questions are specific, because you'll use your research question(s) to guide you in writing a thesis for your paper. Ask your instructor to look over your research questions to be sure you are focused in the right direction.