The private party price is what you hope to be able to sell your used car for. A private party sale, if your used car is valued correctly, is always going to get you more than what a dealer offers you in trade-in. However, you do have to to factor in the amount of time involved in selling a used car on your own.
The private party price for a 2002 Dodge Neon with a five-speed manual transmission and a four-cylinder engine with 50,000 miles on the odometer, according to Edmunds.com, is $4,845, or 22% above its trade-in value. Over at kbb.com, its suggested price is $5,660; that's 35% above its suggested trade-in price. Again, split the difference and mark your price 28% above the suggested average trade-in value of $4,068. That gives you a price of $5,207.
Once you've classified your car and come up with a price, add at least 10% to it. This is going to be your wiggle room. Now that you know what your car is worth, allow yourself some space to be negotiated down on the price. The consumer is going to be the ultimate arbiter of your car's value. Use these guidelines just to get the process started -- to your advantage.
Remember to approach any negotiation with as much information as possible. Always presume the other side is as well prepared as you are if not more so.