If you have a general topic in mind, it's important to develop a basic idea of what's going on in the field. This includes knowing the vocabulary and points of disagreement between scholars. To get this information you might try reading encyclopedia articles. Then you might read some current newspaper, magazine and journal articles to find out how this topic is being discussed currently. See the "Databases" tab on this Guide.
These encyclopedia sources will help you understand your topic and decide on information you need to search for: