In Linguistics essays, whenever you make a factual claim or mention a theoretical viewpoint, supervisors will expect you to provide a source for that information. The source you provide should include the author's surname, the year of publication, and the page on which the information is to be found: this is called the 'Harvard style' of referencing. For example:
... for arguments against see Smith & Jones (1993: 481–483), Chomsky (1995: 154, 286f.; 1997), Vikner (1995: Chapter 5), Rizzi 1997, Iwakura 1999 ...
... and elsewhere (see Seuren 1985: 295–313; Browning 1996: 238, fn. 2) ...
... distinguish certain words from others ‘without having any meaning of its own’ (Hockett 1958: 575).
The precise details of how you present this information vary, and it doesn't matter where you put the commas or the brackets, as long as the key information - author, year, and page - is provided. Referencing like this may seem tedious at first, but it's a useful skill in that it helps you to be explicit about where you got the information from. This skill will come in useful in academia, but also in any job where you're required to summarize and analyse large quantities of information.
At the end of the essay, it's good practice to provide a bibliography in which you list all sources referred to. Again, the precise details aren't important for supervision essays, but below are some examples to help you get the idea:
Akmajian, Adrian, Richard A. Demers & Robert M. Harnish. 1985. Linguistics, 2nd edn. Cambridge, MA: MIT Press.
Blevins, Juliette. 2004. Evolutionary phonology. Cambridge: Cambridge University Press.
Kemenade, Ans van & Nigel B. Vincent (eds.). 1997. Parameters of morphosyntactic change. Cambridge: Cambridge University Press.
Kiparsky, Paul & Gilbert Youmans (eds.). 1989. Phonetics and phonology, vol. 1: Rhythm and meter. San Diego, CA: Academic Press.
Articles in edited books and journals:
Abraham, Werner. 1997. The interdependence of case, aspect, and referentiality in the history of German: The case of the verbal genitive. In van Kemenade & Vincent (eds.), 29–61.
Casali, Roderic F. 1998. Predicting ATR activity. Chicago Linguistic Society (CLS) 34.1, 55–68.
Hornstein, Norbert & Amy Weinberg. 1995 The Empty Category Principle. In Webelhuth (ed.), 241–296.
Iverson, Gregory K. 1983. Korean /s/. Journal of Phonetics 11, 191–200.
Roberts, Ian & Anders Holmberg. 2005. On the role of parameters in Universal Grammar: A reply to Newmeyer. In Hans Broekhuis, Norbert Corver, Riny Huybregts, Ursula Kleinhenz & Jan Koster (eds.), Organizing grammar: Linguistic studies in honor of Henk van Riemsdijk, 538–553. Berlin: Mouton de Gruyter.
Don't use footnotes for referencing, as is the norm in some arts subjects. Footnotes should be used very rarely, and only if you have an important point to make that would detract from the flow of your main argument.
How should I use quotations/examples?
Quotations demonstrate that the point you are making is indeed relevant to the text you are discussing. They are the evidence which sustains your argument. There are no prizes for extensive quotation, especially under exam conditions and many guidelines for authors have instructions advising against quotations that exceed 100 words. Essay writing is not a test of how much you can memorise, but rather of how well you have understood a text's key preoccupations and approaches. To this end, you should learn to use quotations to help you condense a particular point, to illustrate it clearly and pithily.
Quotations must be introduced properly in the body of your essay. It is not enough simply to stick together a point and an example quotation; you must make the quotation fit into the structure of the sentences around it. The principal ways of doing this are:
'...il y a des cas ou même un système très complet de flexions distinctes ne suffira pas à nous tirer d'affaire. Cela arrivera surtout à la troisième personne, ou l'on peut se trouver en présence d'une série de terminaisons de même valeur alors que pourtant les sujets sont différents.' (Foulet 1928:198)
Otherwise, they can form part of the body of the text.
Although isolated examples can form part of the body of the text, in syntactic essays in particular the practice as exemplified in (2) should be followed. Examples of the target materials or structure are often necessary for your reader to be able to follow your argument. They also demonstrate that you have understood what the key data are. However, make sure that you use one example for each issue you wish to discuss – a list of redundant examples can be as under-informative as no example. If examples are presented in a language other than English, then make sure that you include a 'gloss' (word-for-word translation) as exemplified below:
Ele vai ao cinema (Brazilian Portuguese)
he-NOM go-3SG to+the cinema
‘He goes to the cinema.’
You should always include the name of the variety in a parenthesis above or more commonly to the right of the example.
Point to note:
Some students introduce too few examples in their texts, thereby making it incomprehensible to the reader. Think carefully about where exemplification is needed and choose the examples well.