There are two ways to describe detail in a setting:
1) Forest to trees: With this method, you start with the big and work down to the little. For example, your character sees a house. Notices it’s red brick. Has a white porch out front. Sitting on the porch is a flower pot filled with orange flowers. A hummingbird hovers over these.
2) Trees to forest: This method is exactly the opposite. The character sees the hummingbird first. Then the flowers, the pot, the porch, the house.
What you don’t want to do is jump from one method to the other. You don’t want to see the hummingbird, then the entire house, then the tiny flowers, then the porch. Why? Because your reader is trying to focus as you describe a scene. It’s like a movie camera panning in and out. The camera is supposed to start far away and pan in or start close and pan out. If the camera went IN OUT IN OUT really fast, the audience would be left dizzy and confused.
The next question to ask yourself is which method to use when. I find it generally depends on how the character is seeing the setting. If they’re slowly approaching from afar, they would definitely use forest to trees as that is how our eyes work. But if they’ve just woken up and are surveying the scene immediately in front of their eyes, they’re more likely to do trees to forest.
The last thing you need to ask yourself is about speed. Much like the panning camera, the speed at which you give detail dictates the speed at which the character is observing. So if your character is out for a leisurely stroll, they would probably spend a few minutes looking at the detail on someone’s porch, which means you probably want at least one sentence per thing they’re observing. On the other hand, if they’re flying by in a Z4, they’re likely to only see a quick blur which probably means only one sentence or a series of really short sentences.
TIP: If you’re not sure how much time to spend on detail, try reading your description while acting out the motion. If you can’t read it in the time it takes your character to perform the action, it’s too long. And if you’re done reading and they’re supposed to be standing there staring for another five minutes, it’s either too short or you need to transition to another scene.