Obtain as much information relating the subject area as possible and then plan the essay. A good review article will provide a wealth of references and whilst controversial, Wikipedia will also provide a basic understanding and some useful references to explore further.
Plagiarism is not cool and it is simply not worth taking the risk, reference all cited information that is provided by others.
An essay follows a structured format: the introduction, the main body of the text and a conclusion:
The subject of the essay is introduced clearly and succinctly. You will state the key points that will be discussed to address the essay topic or question, giving the reader a brief but clear understanding of the subject area and how you will approach it.
The introduction is not always written first but this is a personal choice.
The main body of the text will be built from paragraphs that will form an argument and/or discussion based on a review of the literature/material available on the subject area. A careful balance between presenting facts, your interpretation of the facts and the interpretation of others is required. You must ensure that all cited factual statements are appropriately referenced. Your argument will be carefully considered and you will demonstrate a critical analysis of the literature rather than the ability to recall facts.
The use of transition words, will allow the sentences and paragraphs to knit together seamlessly. For example: firstly, in addition, moreover, furthermore or similarly, likewise, equally. These provide a connection between ideas and paragraphs enabling the reader to follow a logical argument.
This is aimed at drawing the whole essay together. Do not introduce any new ideas in the conclusion, it is a brief summary enabling the reiteration of the key points raised and areas that require further explanation or research.
Remember to include your reference list/bibliography and finally, pay attention to detail before handing your work in.