Not sure how to reference? Do footnotes, endnotes & bibliographies give you a headache? Then you may like to have a look at Cardiff University's Information Literacy Resource Bank.
It has a whole section dedicated to how to cite references. APA, Harvard, OSCOLA & Vancouver styles are all covered at:
In addition, within the Subject Guides part of the Birkbeck Library web site is a section on Study Skills. This includes information on books held in the Library that you may like to consult, as well as web sites which cover citation.