An advanced method of getting better at writing descriptions is to choose an author you admire and study how they do it. I call this an advanced form because the goal is not to imitate what they do, but to absorb it. That will happen over time and your brain will transform what you learn into your own style of description, not just an imitation of someone else's style.
Let's look at an example. This is an early paragraph from Hilary Mantel's novel, "A Change of Climate." Ten-year-old Kit has just walked into the kitchen to find a woman named Joan cutting her wrists over the sink:
"The woman allowed herself to be led to a chair at the kitchen table. Kit pulled a clean tea-towel out of a drawer and wrapped it around Joan's wrist. The towel was a checked one, red and white; Joan's reluctant blood seeped black against the cloth. Her cuts were light, early, indecisive: the practice cuts. 'Just wiggle your fingers,' Kit said. 'make sure you haven't done any damage.' The woman looked down at her hand in dry-eyed dread, while the child scrambled on a stool and brought down a box from a cupboard."
I like the simplicity of her descriptions. "Reluctant" blood already tells us the cuts are not deep, and that's confirmed by the trio of adjectives: "light, early, indecisive." "Dry-eyed dread" tells us that the woman is going through the motions, she's not hysterical.
Also notice the lack of descriptions of the girl. What we know is that she is handing this situation very calmly and maturely. That makes us wonder who she is and why she's so capable--we want to continue reading to find out, which is the goal of all writing, to make the reader keep reading.
To be aware of an author's descriptive techniques you really have to read a book at least twice, once for enjoyment, the second time to be aware of how she creates the effects she employs.