How can I ensure I actually answer the question?

The most important thing to do is read the question at least twice!  Make sure it's clear in your mind what the question is asking.  Think about the five W's: who, what, when, where and why, as well as how.  'How', 'In what way' and 'To what extent' are excellent analysis questions; you have to ensure there is a clear analysis and argument being made in your answer.  You may do this through making a quick plan or mind map so you don't forget the ideas that come to you when you read the question.  That way, when you come to write the answer you have all of your ideas clearly in front of you and can create an excellent line of argument from it.

In exam conditions you may not have the time to read through and check your answer.  However, with coursework and essays it is important to ensure each paragraph relates to the question that has been posed.  It is easy to lose track of the question but by doublechecking you are improving the accuracy of your answer.