Yesterday I saw a pickup with the driver's door open. On the floor was enough dirt, grass and debris to fertilize and start a lawn. There was a "For Sale" sign on the side window.
I see stuff like that in variation everywhere, even here. People show engine compartments that are plain filthy. Makes me wonder what their dwellings are like. I say a very important, critical issue when selling is to present a near-perfect vehicle to potential buyers. Even clean under the vehicle, fender wells, engine compartment, bed, floor etc. Not only clean but waxed and scented. I personally hate to sit in some vehicles because the seats flat out smell and are soiled. I had a chance to buy a fellow's Cummins used at a good price but declined. Declined because I knew he had incontinence issues and soiled his seat at times. You could smell things like that, along with smoking smells.
Present a perfectly clean vehicle, decent service records, good tires, oil etc. Then you have a good chance of someone taking a measure of pride in wanting to buy your offering. If that is not something a seller can do, that seller should not expect an positive experience from potential buyers.