A way to improve this would be definitely to do relevant past short answer questions from vcaa exams. When checking the assessors report, they usually mention what was required for full marks.
You could make note of the types of things you were commonly missing and see if there are any patterns, e.g. including examples. Then you could work on these things.
Also, I found that many of the future questions rely on similar knowledge. e.g. When explaining biofeedback (not sure if thats still in the study design) I think I remember there being three distinct parts you had to refer to (if it was a three mark question). I had I learnt this from a past assessors report and it happened to turn up in one of my sacs (so I was able to perfectly answer the question).
Other than that, just put yourself in the mind of assessor when answering a question.
As was already mentioned by PhoenixxFire, just pay attention to command words and you can even highlight key terms (e.g. 'using an example' -- definitely don't want to forget, or 'list one advantage, one' blah blah) so that you don't ignore key parts of the question.