I used to have a critique partner who was really good about examining each scene for the sensory details that were missing. For example, when a couple of characters walked into a kitchen where a woman was cooking, and I hadn’t thought to describe the smells.
☐ All senses are engaged as appropriate to each scene.
Try not to obsess over this kind of detail early on, but once you reach the polishing stages of your edit, run down every scene and consider all five senses: is there one that belongs there that you’re missing?
Vision: We usually get this one right, because even verbal people like writers tend to think “camerawise,” that is, describing what a camera would see if the book were a movie. But go a little further and consider things like what time of day it is—at what angle does the light hit the windows? Is it bright midday light, or the golden light of late afternoon?
Sound: Some noises are so loud you feel it in your bones. Others are so quiet you strain to hear. Every setting, even a library, has ambient noises. Describing those background noises will help set the scene.
Smells: If someone’s in her own home, she’s unlikely to notice the smell unless it’s different from usual. Maybe the trash has gone rancid, or her husband is cooking something spicy. But she’ll notice the smell of her neighbor’s home, even if it’s just because the neighbor uses a scented laundry detergent.
Taste: Not only the taste of food or drink, but think about how the air tastes when there’s a fire upwind. Or a dusty, windy day when you can taste the dirt in your mouth. In the autumn, when the weather turns cool, the air doesn’t just feel and smell different, it tastes different.
Touch: When your heroine curls up under her favorite blanket to read, is it soft wool from the best shop, or scratchy acrylic yarn her grandma bought at K-mart? In fight scenes, don’t just show the punches, describe how it feels to be hit. And remember that the knuckles of the one doing the punching usually take a beating as well. Another feeling that’s easy to forget is the feeling in your joints when you’re doing some activity. Whether your hero is surfing or skiing or riding a horse, he’s going to feel it in his muscles and joints. Try to capture that sensation for the reader.
Run a sensory check on every scene. Sometimes the answer will be no; there’s nothing unusual to feel or hear or smell. Don’t distract the reader by putting in irrelevant sensations just to tick an item off a list. But often a sensation will come to mind that fits, that amplifies whatever the viewpoint character is experiencing. Those are the details you want to add.