The search terms or keywords you use to search are what determine the results you get. Here's a good exercise to help you generate keywords:
1. Express your topic in a topic sentence: “What is the effect of television violence on children?”
2. Generate keyword search terms by identifying the main ideas or concepts within that topic sentence: “What is the effect of television violence on children?” = Effect, Television, Violence, or Television violence and Children
3. Expand your search terms by brainstorming related terms or synonyms that describe your main ideas: