What structure should I use in the essay section?

The LNAT essay should have a similar structure to an A-level humanity essay (especially English or History). You will have to consider both sides of the argument before coming down on one side with sufficient reason in the conclusion. Considering that you only have 40 minutes for the essay, of which 2.5-5 should be used for planning, you will have less time than you are used to. Therefore, the structure should remain as simple as possible: introduction, paragraph to agree/disagree, second paragraph to agree/disagree, and conclusion. A good essay will answer the question in the introduction, outlining the main arguments, and establishing the conclusion. The main paragraphs should consider both sides of the argument and each be filled with plenty of evidence (which can remain vague as you are not expected to know any facts), and the conclusion should be short and simply come down strongly on one side, preferably by once again outlining the main argument. Ending with a simple, summarising sentence is also beneficial, but not necessary.