How can I improve my essay-writing?

Although the HAT papers say that you need no prior knowledge for the test, it's actually very helpful to learn as many facts as you can about a few topics. This is because an essay cannot be good if it is not grounded on concrete evidence, especially in history. That's also very important because examiners will appreciate it if they see that you can bring in a subject you are particularly fond of - showing knowledge of detail is a way to demonstrate that.