Yeah I'd agree with the HSC marker, heh. I've done Modern History in year 11 and 12, getting a few 100% marks along the way! The way to get the good marks is simply to know the syllabus back to front. Know dates, figures, places and events - that way, if it's a question say about trench warfare, or a question aimed at changing attitudes of the war - you can mention relevant material.
Less is more as they say. You don't always need to throw everything you know at the question. Just go on the related points, and expand on them. This is the same in English. In depth relevant analysis beats brief overviews any day.
Hope it helps.