I look at several aspects when describing settings:
It's helpful to look at each of the senses in turn and make a few notes on relevant things in the setting to each of them, basically answering the following questions:
What can the character see?
What can they taste? (might be something on the air, rather than going around licking trees and walls and stuff)
What can they feel? The texture of things around them, temperature, weather...
What can they hear? Close by and far away sounds.
What can they smell?
When describing a place, think about how each element can be interpreted. For example:
The house could gleam brightly with a fresh coat of whitewash; have aging, peeling, lead-heavy paint; or give the impression of a gaping skull with sightless windows as eyes and a door forever gagging its silent scream.
The sea could roll heavily, recline in reflective tranquility or froth with lively white horses.
The way you describe the scene shoudl reflect the mood and atmosphere you're trying to evoke in the reader.
When describing locations, I'm always considering what the POV character would notice about it. For example and ex-police officer is likely to notice completely different things to a five year old. What is important to the character? How do they feel about different places and the furniture and others items they might come across in those places?
You also asked about motivation reaction units, and whether you can use them. I think these relate more to character and driving the plot than setting description, so trying to apply them to your descriptions might get a bit confusing. Personally, I wouldn't try.