An interior done out of order gets done twice. Dust falls on cleaned carpet, shampoo soaks a seat you already conditioned, and the air freshener goes in before the smell is gone. Here is the order that works.
1. Remove and dry-clean everything
Mats out, trash out, seats slid forward and back. Blow out the vents and seams with compressed air, then vacuum top to bottom with a crevice tool. All of the loose dirt leaves the car before any liquid goes in.
2. Hard surfaces, top down
Headliner edges, dash, console, door panels. A dedicated interior cleaner like P&S Xpress wipes plastic, vinyl and screens without leaving a shine. Spray the towel, not the dash, so nothing mists onto the glass. Use a soft detail brush in the vents and around buttons.
3. Fabric and carpet
Pre-treat stains, then clean the whole panel so there is no tide line. P&S Carpet Bomber is the extractor-strength cleaner for carpet and cloth; agitate with a brush and extract or blot. For a single stain, a spot cleaner saves soaking the whole seat.
4. Leather
Clean leather with a leather cleaner and a soft brush, never with the carpet product. Wipe dry, then condition with a thin coat of P&S Leather Treatment. Thin is the whole trick. Thick coats sit on top and attract dust.
5. Glass
Glass goes last because every earlier step leaves a mist on it. Two towels: one with the cleaner, one dry. Roll windows down an inch to get the top edge.
6. Odor, at the source
If the car smells, something in it is still producing the smell. An enzyme product like Ardex Enzyme Digester eats the organic source in carpet, fabric and vents instead of covering it. Apply it after cleaning, while the fibers are still damp, and let the car air out.
The whole kit is in Interior Care, most of it in gallons.