One skill a writer needs to learn is how to be objective. Objectivity is important so you can describe the world and make seem real or true. This is true even when you story is from a distorted point of view because if I don't believe the events a plausible I lose interest and read something else.
Exercises for being objective are straightforward. For example, find a spot where you can observe something and describe it. If you take public transportation, you can practice this on the bus or subway. Observe the people around you; describe them in a few words.
Or go further, give them fictional backgrounds based on what you see and observe about them. This one is a little more interesting and requires a little deductive reasoning along with observation.
So the man in the corner of the subway train who is always reading his Kindle seems to lead an ordered life. His ID badge to a local hospital shows his shows is quite busy and his 15 minutes on the train reading is probably the only peaceful he has.
This man follows a deeply set routine, probably because his job is very fluid or because his job requires he follows a strict set of procedures, possibly both.
He dresses well and since his hair is going gray, I assume he has done his job for many years and his acquired some wealth as a result.
He sits in the corner away from everyone else so he is not disturbed while reading.
I have no idea if he is married or divorced but he is a very orderly man.
That's a quick sketch of one person from the subway train is sometimes ride in the morning. It gives you an idea of the man and is enough to round out if I want use him in a story. I still need to describe his mannerism, his appearance, and so on. I need to give him a name and set him somewhere plausible so that as a character in a story, he is believable.
That's no small task because such an orderly man probably doesn't lead a very interesting life, at least from the perspective of telling a story. There's probably no action or drama in his life, which means no story. Oh I can probably think of something to change that but I have to be careful because too much drama and I change who this character is. Not enough and I bore the reader.
So observe, describe, and be objective about world and everything around you. And above all, keep writing.