How do you structure and write a history essay to maximize marks?

The best way to structure your essay is to break your essay up into roughly three sections. An introduction section. A main body section. And then a conclusion section.
Your introduction should briefly set the scene, normally with one or two sentences giving a bit of detail about the time period and the historical significance of the question being asked. You then want to answer the question in one sentence and pick 3 or 4 points which show your answer is correct. The main body should then build on these 3 or 4 points, fleshing them out into paragraphs with evidence, historical facts and figures. One of the points should show you are aware of disagreeing points of view with your argument but though you have considered them, there is evidence which means you find them unconvincing. The conclusion should then summaries your argument and restate how you have shown your answer to be justified.