I keep my car relatively clean and tidy.
There is always 1 car seat in the back, because I take one of my young granddaughters to her preschool Mon, Wed and Fri. Sometimes there's booster seat too, for when I take two of my younger grandkids for an outing.
Other than that, there are some things I keep in my car routinely. A cardigan (I am in and out of client's homes, and sometimes I freeze!!) In the doors, or the console on the dash I keep sunglasses, hand sanitizer, an extra pair of glasses, hand lotion, gloves, extra napkins and a small trash container. In the center console I keep chapstick, scissors, nail clippers, extra car air freshener inserts (I have a holder that clips to the air vent) lens cleaner, tape measure and a multi tool.
In the trunk I have a small crate that holds the things I use to when I take my car to be washed...window cleaner, paper towels, some soft micro cloths, spray cleaner. I also keep my re-usable grocery bags in there, plus a soft pad made especially to put down in a store cart for when I take my dogs to the pet store. They're tiny, (3 lbs each) and their little paws would slip through if they weren't on something.