Referencing your work correctly is essential. If you acknowledge the work of others you are taking steps to avoid plagiarising someone else's work. You are also allowing the reader to trace your line of research.
There are three fundamental types of referencing styles: Author/Date (e.g. Harvard), Numbered (e.g. IEEE or Vancouver) and Footnotes (e.g. MHRA). Using software like Endnote to manage your references can help.
Different disciplines will recommend different referencing systems so do check with your tutor. Once you know which system you are using it is important that you are consistent.
Note some of these have both been withdrawn without an updated standard being issued. They are potentially still useful, but should be used with caution unless specifically recommended by your discipline.