Even though time may seem short in an exam, it is important to take a few minutes at the start to plan your answer. This will help you save time later and will make sure your essay is coherent and well-structured. In this case, it might be helpful to have a quick brainstorm of the main factors involved in causing the Civil War. It is probably best to start with “Charles I’s political failings”, however as this is a “how far” question, examiners will be expecting you to compare this with other factors. For example, in your brainstorm, you may decide that you will also discuss religious issues and also the role of Scotland and Ireland. Your overall argument and introduction may therefore be something along the lines of: Charles I’s political failings played a significant role in causing the English Civil War but only in conjunction with mounting religious tensions which sparked rebellions in both Ireland and Scotland and it was these which acted as the trigger cause in leading to war in England.
Within this, you are not only explaining what caused the Civil War but giving weight to each factor and therefore answering the “how far” part of the question. At the end of each paragraph/point it is important that you refer back to the question and this assessment of the importance of each factor. For example, at the end of paragraph 1 discussing political failings, you may write “Charles I’s personal rule which allowed the arbitrary levying of ship money certainly caused discontent, but this alone was insufficient to lead to war. Rather, the effects of his political miscalculations were exacerbated by his religious measures such as his attempt to impose a new Scottish prayer book in 1637”. Spending that 5 minutes planning means that when you start writing your essay you already have your argument in your head as well as the three main points which you’re going to discuss in the bulk of your essay.