Here are situations in which you must cite:

1. Using obscure or newly discovered facts.
2. Using someone’s opinions.
3. Direct quotations
4. Paraphrasing someone else.
5. Summarising someone’s argument.

Why cite? The purpose for citing is so you do not have to make that argument and present that evidence.  If the reader is puzzled by what you say, or wants to know more, or wants to see a justification, they can use the citation to find the source you referenced and asess it for themselves.

Citations help your arguments.  Effectively, you are saying “I accept what this person says, and I’m moving on from there.  If you don’t like it, your argument is with them, not me.”  For example, if you want to say that capitalism is evil and discuss alternatives, you’ll have to first explain how and why capitalism is evil.  On the other hand, if you say that you accept Marx’s arguments for the evil of capitalism and are now going to discuss alternatives, anyone who doesn’t believe capitalism is evil has to argue with Marx, not you

Referencing is letting the reader know where you got the information from. The text which does this is called a ‘reference’. ‘Citing’ is another, more formal, term for referencing. Under this terminology, a reference is called a ‘citation’. A citation is the same thing as a reference.  Universities prefer to talk of ‘citations’ rather than ‘references’.

Referencing is one of the most emotionally difficult parts of learning to write for university, but unavoidable. It is fiddly, pedantic, demands concentration, can be hard to learn, yet it is absolutely vital you master citing. Every person marking your work has been through the same pain, and mastered the skill. They will be sympathetic to your pain, but won’t relax their demand that you cite correctly, even in your first written work.

Each department can decide which style to use.  Some departments allow each lecturer to select their own preference.  Most departments will list the citation style in their handbook.   Do not guess.  If you are not absolutely clear as to which citation style is expected, ask.  Be careful.  There are many versions of some citation styles, so you need to ensure you use the version the department demands.  Some citation styles are updated every year, but a department may stay with the same old version for 10-20 years.

Your first port of call for Referencing guidance should be your Department's handbook.

But you can check out the Library's Referencing guide for help laying out your references.

If your work demands research, it must contain a bibliography.  Some disciplines, such as Education and English, have “reflective” essays, in which people discuss their internal thoughts.  These do not needcitations, but a few citations may improve your marks.  All other written work will require a bibliography of citations used. 

Bibliographies should contain only references you cite in your work.  They are not places to list everything you read, only what you use.  Essays are not assessed on the effort you put in, only on the results you produced.

Don’t provide too many direct quotations.  Many academic journals set a limit of two.  You will not get any marks for including quotations at all – you didn’t write it so you can’t get credit for someone else’s work.  Quotations take space you could have used for your own writing, which you will get credit for.  If you put too many quotations into your work, you give the impression you are just filling it up because you couldn’t think of anything to say.  When you do use a quotation, keep it as short as possible.

There are only two valid reasons for including a direct quotation. 

1. Use a quotation if you want to discuss it and need to refer to the words used. 

2. Use a quotation if it says something so perfectly you could not possibly do better (which is rarely the case).

It is always preferable to paraphrase a quotation with your own wording.  Not only does this maintain originality, it demonstrates your understanding of the original quotation, which improves your marks.