It is important that your essay has a clear introduction, main body and conclusion.
Put simply, you should:
• Say what you are going to say (introduction)
• Say it (main body of essay)
• Say what you have said (conclusion)
The number of paragraphs in the main body of the text depends on the topic, the discipline, and the number of words you have to write. First and last sentences of paragraphs are important signposts as to where your essay is going. First sentences should tell the reader something clear and specific about the point you are about to discuss. Last sentences should make the relevance of the point totally clear. The crucial feature of the structure is that each paragraph only contains one main idea.
Below is one example of the structure of an essay:
• Group similar ideas together rather than jumping around.
• Individual paragraphs should be differentiated typographically, i.e, by indenting or by allowing additional line spaces between (check whether your school has a preference).
• Think of paragraphs as mini-essays. Start with a topic sentence to introduce the main point of the paragraph; explain that point further; provide evidence and interpret/analyse the point; then link it to your overall argument.
• Each paragraph should link to the next using transition words or phrases, such as 'alternatively;' 'consequently;' 'as a result'; ' furthermore...'
• The paragraphs should be placed in logical and consistent order. Play around with them until you get the best flow. They should feel progressive rather than list-like.
It is useful to know what you want to argue before you begin to write. State your argument in your introduction, and then spend the conclusion summarising the reasons and evidence that make it valid. Again, signposting here is a key skill.