Be selective when choosing sources to include in your review.
Start by looking for documents that highlight major developments and theories on a topic. Look for documents that generated significant contributitons to the field of study. Ensure coverage of all sides of the topic.
A good strategy is to start with the most recently published sources on your topic and search backwards. Recent studies will mention major crossroads and developments in the field, more recently and often historically. Depending on your topic, your literature review may cover some historical background with more focus on recent research, or it may cover recent and historical findings equally.
Use a range of resources including books, journal articles, websites, theses, conference papers, government document and reports to compile information on your topic.