When I'm in the exam, how can I answer a question accurately in a short space of time?

When you're answering a question- don't panic! Panicking will stress you out and slow you down.  When answering a question- answer the question.  Going off topic is where students lose marks and time.  For example, when asked about Localisation of Function (10) it is important to remember the acronym SEXY! State, Explain, Example, Why.  So in the Localisation of function question, for example, you will want to State the explanation, explain what the LoF theory consists of, give an example (for example, Broca's area), and then link back to the question! 

Your answer will be no more than 12-14 lines long, and your question will be answered to the fullest- gaining you those high marks.  Its all about planning!