Pre-searching your topic means looking for background information to help form your understanding of your topic. Pre-searching can introduce you to relevant vocabulary, people, places, events, and ideas related to your topic--all of which might inform your research question and help you build a list of terms to search once you actually start searching for resources that support your research question.
Some good places to start gathering background information are Wikipedia andGoogle, as well as magazines. MasterFile Premierprovides access to thousands of magazines and journals, among other resources that might be helpful when you are just getting started. Here is a list of magazines that might be good places for you to begin looking:
GVRL is a collection of online books that you can search all at once. There books here are on a wide range of topics, not just communication topics. This is useful for getting background information on historical events or topics that may have a non-communication dimension, such as health issues or political issues.