There are many things you can absorb from listening to a reference track: rhythm, form and dynamics just to name a few.
Lately I’ve been getting into the habit of writing out what I call the tone palette of a song. It’s simply writing down how many instruments and what they are in any given production.
A painter doesn’t usually paint with every single color. They make specific decisions. Production is no different — you have to consider that the instruments aren’t always individualized. They congeal together. This is the goal in a great recording: when everything becomes one.