prompter: I'm running a mystery adventure for my tabletop rpg group. I want the players to discover that the abandoned car that is thought to have been last driven by its missing owner was in fact driven by someone else. What kind of clues could I provide to lead them to that conclusion?

assistant: Here are some clues you could give:
The driver's seat and mirrors could be adjusted differently, hinting to a different anatomy of the driver
The air in the car could be filled with a certain smell hinting to a different person (like an aftershave, if it is a male instead of a female, or a smell associated with a certain working environment like a kitchen, or a fish market)
There could be direct traces, like a lost hair, a shoe print, or hand print, that wouldn’t match the owners physique

assistant: Here are some options for clues to show that the car was driven by someone other then the owner:

You could indicate that the seat position or mirror alignments were calibrated for a person much taller or shorter then the owner.

If the owner had particular dietary requirements, you could show fast food wrappers contradicting that.

You could even show that the driver was listening to music completely contrary to the owners taste, such as the CD in the player being of a genre they owner hates.

prompter: Great! Can you give me some more ideas?

assistant: Of course, here are some further suggestions:

Perhaps the car has signs of forced entry, showing it may have been stolen.

Maybe this person is messier or cleaner than the car's owner and there are signs that show this.

If your players are able to analyse fingerprints in the game you are playing, you could have fingerprints differing to that of the owner on the steering wheel or door handle.

assistant: You could leave additional identifying information, such as a footprint or even an ID of a person other than the owner by or near the car.  The kind of clues you use depends highly on the players that are participating in your RPG group. Be mindful of their level of awareness. Some clues are better suited for younger and less experienced players, such as a driver's license of someone other than the owner of the car.

assistant: You could let the users rise some doubts on the last driver of the abandoned car by giving some low profile hints.
In example you could describe what was found inside the car, in detail, and highlighting some object that is in contrast with what the thought last driver was .
To be more explicit, you could describe a women perfume bowl ( that seems used little time ago ) while the intended driver was a male.

assistant: There are many ways to hint at that, depending on your situation. You could try to use one of these:
- Make the owner have an alibi. Some sidecharacter could hint at that
- The real driver could have left something in the car that could be connected to them. A hat, for example.
- If a dog smells the car, it doesn't connect it with the real owner.
- Make the owner have a habbit that isn't fulfilled in the car. Always leave gear stick to 1, for example.
- The car could have been seen somewhere where the owner has no reason to be (or can't have been)

prompter: I like the idea of giving the owner a distinct habit that doesn't line up with the state of the car. Could you give me some ideas on what that habit could be? Preferable it's a habit that is applicable in a lot of situation, so I can really reinforce that information repeatedly during the game.

assistant: Sure! Here are some ideas:
- Reveal that the owner has a strong dislike of cigarettes, and have the real driver be a frequent smoker with a preference for a unique brand. Leave some cigarette butts in the car (and in other places where the driver may have been) and let the players find them.
- Make the owner very short, to the point where they need some sort of booster in their car seat in order to drive safely. Then have the players discover that the booster is missing or removed from the driver's seat. The owner could not have driven the car without the seat, so the real driver must have been tall.
- Make the car's transmission manual, and suppose that the real driver only knows how to use an automatic transmission. By examining the car's shifter and transmission, the players will discover that the driver damaged the transmission in confusion. Since the owner knows how to drive a manual car, the real driver must be someone else.

assistant: Sure, here are some habits you could use:

1. Always leaves the passenger side mirror in a specific position.
2. Always keeps the radio on a specific station.
3. Always keeps the cup holder filled with a specific drink.
4. Always keeps the seat adjusted to a specific position.
5. Always keeps the air conditioning set to a specific temperature.
6. Always keeps a specific item in the glove box.
7. Always parks in a specific spot with the wheels turned a certain way.
8. Always leaves the sun visor in a specific position.
9. Always leaves the windows open a certain amount.
10. Always leaves the car in gear (park, reverse, etc.).

assistant: Okay:
- position of the seat too far forward or back, or reclined
- mirrors could be aligned to a different viewing height
- the odometer is too high for their usual route
- the tires appear to have residue form somewhere out of the ordinary
- service records show unknown visits to the shop
- fuel level is too low and the owner usually keeps it much higher
- the body is scratched or dented
- the radio stations are all wrong
- it smells like perfume, cigars, or anything unusual
- they left a package behind
- forensics