Choosing the correct style for your purpose will be directed by your discipline, publisher or university. Schools at your university will provide a style guide outlining the style they utilise and the required format. There can be slight variations in format despite being the same style, so it is important to check even if you are using referencing software. Consistency is a key feature in correct referencing.
A number of styles exist in referencing. They usually fall into two categories:
Heart disease is Australia's biggest killer (Smith, 2010).... OR
Smith (2010) has shown heart disease is Australia's biggest killer.
Smith  has shown heart disease is Australia's biggest killer.
Some of the more popular referencing styles are: