Sensationalism is one of the major causes (or perhaps results) of media bias. It stems from the fact that the news media depends on viewers for financial support, and thus the media is likely to report stories that are likely to draw in high numbers of viewers, even if the stories do not have much news value. Examples are celebrity gossip, sex scandals, and crimes committed under bizarre circumstances. The result is that many important stories go underreported by the media.
A common theme in sensationalist journalism is to print a dishonest headline that either omits and important truth or makes a deceitful generalisation, and then print the actual truth in the article (usually burying it near the bottom).
Emotional words are also often used in headlines.