Spend about five minutes thinking about your answers before you begin to write. Organise your ideas and jot down an outline. A few minutes spent in this way will help you to write a coherent essay with a good introduction and conclusion, and will save you a lot of time in the end. Don't forget a summary and general conclusion. It's better to write less, but legibly, than to write a lot, illegibly.
Bad handwriting can be very annoying to markers.
Get the key points down. If you run out of time, use dot-points to get your main points down. After the exam It can be helpful to have a look at your exam paper after it has been marked. You might like to discuss that question with your lecturer or with a study skills adviser. However, university regulations mean that you cannot take your exam paper away or photocopy it.