I would just get a list of buzzwords if you like that you can apply to extracts with reference to each of the concepts - especially contrasting ones e.g warm lower register contrasts the cold, harsh upper register etc.
I jot down bullet points and then write a little essay thing, maybe structured bullet points is better overall anyway.
I reckon first thing you should do is identify the instrument entry order, and then see where that takes you - range, layer, role, melody etc
This then leads to overall tonality and structure - structure often identified by dynamics etc.
If unsure just write aerophone, chordophone etc
If unsure of exact time signature it could likely be changing.
Just practice - that's the best way to get better, just do past HSC papers.