The most important thing is to have a decided what you are trying to argue before you start writing. Once you've got a clear line of argument you can use the essay to constantly build up the evidence to make your argument as convincing and well thought-out as possible. The essay needs to be broken down into paragraphs which each have their own 'factor' which supports your conclusion. If you were asked how a government achieved a certain objective, you would want to break your essay down into the different ways that they reached their goal, these might include military strategy or propaganda for example. In these paragraphs it is important to remind the reader or examiner of the effect of these factors and how they contributed to the governments objective. Make sure you support statements with evidence and knowledge. When you are writing your essay, try to imagine that the paragraphs are the building blocks for your overall argument, and everything you write should be strengthen and solidify this argument.