It is difficult to define a topic with much specificity before starting your research. But until you define your topic, you won't know where to begin your search for information and you won't know what to look for. With a well-defined topic, you can focus your search strategies to find lots of relevant information without also finding a lot of useless stuff.
Selecting a topic to research is not a one-step task. Identifying and developing your topic is an ongoing process that does not end until you have finished your research project. Start with an idea you are interested in. Find and read some background information to get a better understanding of the topic, then use what you have learned to search for more specific information. Refine (broaden, narrow, refocus, or change) your topic, and try another search.
Find a Topic
If you weren't assigned a specific topic and can't think of one:
Narrow Your Topic
The initial idea for a research topic is often too broad. If your first searches for resources are so general that you find more information than you can click a mouse at or deal with in a reasonable amount of time (i.e. before the research project is due), focus on one of the following:
Make it a Question
It is often helpful to state your topic in the form of a question. Treat the research project as an attempt to find a specific answer for a specific question.
List Main Concepts
Pull out ideas and key terms that describe your topic. You can get a better idea of these by looking up your topic in an encyclopedia or other appropriate reference work. This will give you a better understanding of your topic, which will help you figure out what sources you will need and where you will need to look to find them.
Analyze Your Topic
Where should you look for information? From what subject or discipline perspective are you looking at this topic? Do you need scholarly or popular sources? Will you need books, articles, sound recordings, primary sources, etc.?
Select Appropriate Tools
Which tools do you need to find the type of information you want, (e.g. the library catalog for books, subject specific indexes for journal articles, etc.) See the library's guide to How to Find and Evaluate Sources for more.
Initial Results
After you do an initial search, you can tell some things just from the number and type of sources you find. If you get a million or so hits, you probably need to narrow your topic. If you get only a few, broaden it. If the hits seem to be irrelevant to your topic, search using different terms. Do another search and see if you get what seems to be an appropriate amount of appropriate sources. Keep refining your search until you are satisfied with your results. Then go read them.
Revise
After reading through some of the sources you find, you will get a better understanding of the topic you are researching. With this better understanding, you can revise your initial topic and its corresponding question for which you are so diligently seeking an answer. You can also refine your search strategy: the databases you search in, the keywords or subject terms you search for, etc. Go back and try another search using your revisions. Repeat as necessary until you have done enough research to know what to ask and how to answer it.