If you have trouble coming up with a topic or its keywords:
Check a subject encyclopedia for ideas and concepts.
Do some exploratory searches in an article database like Academic Search Premier. Look at the abstracts or summaries of articles that interest you; they may give you ideas for topics. Also, look at their subject terms for possible keywords.
Check a database thesaurus for alternative keywords and to get ideas for refining your topic if needed. Many subject databases have thesauri such as ERIC (education), PsycINFO (psychology), and Sociological Abstracts (social sciences).
If you need help, ask a reference librarian.