When answering an essay question, the most important stage, in my view, is the planning. Personally, I like to make a mind map, but it really depends on what you feel the most comfortable with, and I recommend trying different options before choosing one. Next you need to come up with your core ideas. Every exam board has their specifications, but usually with history, all examiners like to see a debate within your paragraphs, supplied with historians' quotes, and evidence, with a mini conclusion at the end. I highly recommend jotting these down in your plan, so that when it comes to writing the essay, you can argue each point clearly and firmly, having already come to your arguments in your plan. Finally you can make brief notes on your introduction and conclusion, which I also recommend doing last, as your point of view might change as you write your key points down! It's very good exam practice to just make lots of plans for as many questions as possible, so you become quick at this. It should take you no more than 15 minutes in the actual exam to do.