Getting high-level background information on a topic. This will give you a basic understanding so that you can start more in-depth research.
Familiarizing yourself with any specialized vocabulary used to describe the topic. This will help you come up with more sophiscated search terms and strategies, allowing you to find relevant information quickly and easily.
Use the references list or bibliography at the bottom of the entry. This will point you to more detailed and more reliable information from a variety of sources, such as newspaper articles, scholarly articles, books, book chapters, reports, etc., allowing you to verify any information found on Wikipedia at the source and make judgements about the value of the underlying information.