This is where we develop the skill of listening. Try not to think about it as written work or theory, but more about how you practise the skill of hearing things better.
Practise it just as you'd practise your instrument.
Pitch: Melody & Harmony
Duration: Rhythms and how they are used
Texture: Roles and use of different layers
Tone Colour: Describing the sound
Dynamics and Expressive Techniques: Shifts in volume and instrumental techniques
Structure: Defining sections and how they are used
STRUCTURE: The sections of a song. You must do two things here...
1. Get the sections correct
2. Prove why you chose each section
(What makes Section A 'Section A'; What makes Section B 'Section B'?)
Two contrasting sections
"A-B"
Two contrasting sections, then a return to the first section
"A-B-A"
Three contrasting sections with a consistent return to the first section
"A-B-A-C-A"
A - Theme (ABA)
B - Development (ABA)
A - Recapitulation (ABA)
Coda
A - A - A - A....
A - B - C - D - E.....
A - B - C - D - E...
BUT - a recognisable theme is present in each section which adds familiarity to each section.
Theme - Variation 1 - Variation 2 - Variation 3....
Intro - Verse - Chorus - Verse - Chorus - Bridge - Chorus
...many variations can apply...