Open the driver's car door and look at the interior. Check the seats, the backseats, the carpet, the door carpeting and the roof. Looking at the interior of the vehicle can tell you a lot about what this vehicle has been through and how well the person takes care of their car. People who are usually uptight about their cars and takes care of them will generally keep the interior neat and tidy. People who don't care to wash or keep up with the maintenance on their cars will have spots all over their interior with trash all over the place.
To check for rollback mileage is very difficult. Still, there are a few things you can do to determine if that 96 Accord you are looking at really only has 30,000 miles. One of them is to look at the odometer on the car (only applies to older cars as almost all new cars are digital) and see if all the numbers line up with each other. A untouched odometer would have very low variation in rotation to each other. They should all line up the same way with the exception of the last digit on the right edge. Another way is to look at the wear and tear of the interior. If the interior is falling apart and looks like it's been through quite a bit, it is an easy sign that the odometer has been rolled back. You can also take it to a reputable mechanic and through some thorough inspections, they can give you a strong estimate on how many miles the vehicle has probably been through.
The picture below is a snapshot of the gauge cluster on my car. Notice how the mileage display are all lined up perfectly with the exception of the last rotating number used as a constant calculation for mileage.
One thing to always do is to ask the owner for the keys and make sure all the power mechanics are in working condition such as windows, mirrors, sunroof, locks, air conditioning, heater, radio, windshield wipers and anything else just so that there won't be any unpleasant surprises later. Look at the edges of the door panels to see if it has been removed before or replaced. When people have taken apart a car, you can sometimes tell because it is a tight fitment and you don't always get to put it back to the way it originally was.
