Although the content and information that you put in an essay will change depending on what topic it is on, a logical and coherent structure (part of the mark scheme) is essential in getting top marks.
How it should be structured:
Read the question carefully. What kinds of phrases stand out? i.e. 'Explain', 'Examine', 'Evaluate' - these all lead to various structures and ways of answering the question.
Introduction - key (especially for a 15 mark essay) - provides the examiner a insight into a student's understanding of the context and the key words (which should be defined) of the question. State your argument/stance on the question. Perhaps include a key fact if you have time.
Main body - This may seem overwhelming at first. Make it simpler by choosing thematic/topical points based on the question and following this structure: Point, Evidence, Explanation, Link to the question (PEEL). Make sure that in the point, you are answering the question. Make sure you paragraph and keep the structure clear. This will help you to ensure a clear argument throughout. Provide case studies to exemplify knowledge and to strengthen your points/argument.
Conclusion - Draw together the various points made in the main body of the essay. Summarise the arguments you have made; reiterate your argument and link back to the question.
Notes: Be synoptic! This is key to make sure you get into the top band of marks - shows the examiner that you are well-rounded; illustrates a better understanding of the fundamental basis of geography as an area of study. Timing is important - for 15/20 markers allows for around 20 minutes, for 12/10 markers, aim for around 15 mins. Spelling, punctuation and grammar are important. Make sure you know what the exam board are asking for i.e. Edexcel