When approaching research on a specific topic, the most effective method for searching is often Boolean keyword searching. This technique gives users great flexibility when working in a database, allowing one to combine multiple terms to form a very specialized search statement.
The first step is to consider your topic, and to determine the most important terms to include in your search statement. Let's use the following topic as an example: "Do environmental factors play a role in the development of Alzheimer's disease?"
For this topic, then, the main terms are Alzheimer's disease and environmental factors.