For each module you take you need to find out which referencing system you are expected to use. This may be detailed in your handbook or on the school web pages. If you are unclear about which referencing system you should use, ask your tutor.
The Infosuss website (developed by the University of Sussex) shows how to use the Harvard, Numeric, Vancouver and MLA referencing systems.
Another excellent website is Referencing@Portsmouth. This site covers Harvard APA, Vancouver and Oscola systems and includes detailed examples of how to reference more unusual sources e.g. an article in a newspaper or a musical score.