Buying from a private party can score you a deal on a used car—often discounts of 15 to 20 percent when buying from a private seller over a dealership. However, how do you make sure the deal isn’t too good to be true? Dealer insider, Ed Armbruster, gives his tips on buying from a private seller.

Q. What should you ask the buyer before purchasing?

A. This depends on the age/mileage of the car. If the car is relatively new, with low mileage, you want to know if it has been in an accident, if there are any issues at all with the car, and you want to see any and all oil-change receipts. If the car is a few years old or more, you would want to know if the owner who is offering it is the original owner, and if not, what they know about the original owner. At any point, documentation helps paint a picture of how the car was cared for. Someone who collects paperwork meticulously may very well maintain their car the same way. Finally, ask why they are selling the car: If they stumble around or give you a screwy answer, look closely before buying!

Q. What are some things to look for when seeing the car for the first time?

A. I try to look for evidence of repairs, lack of maintenance, and needed repairs. Mechanically, I look for worn tires, bent wheels, dirty fluids, and oil leaks. (Is the car parked on the lawn? If so, why? Is it so that I can’t see the oil spot?) In the body and paint area, I look for dull paint, swirl marks, uneven body gaps and missing clips on the fascias and in the wheel wells. The same things apply to buying from a private party.

Q. Do you recommend bringing your own inspector?

A. Yes! Or ask the seller if you can take the vehicle to a dealer or someone you trust for a complete inspection. If the seller is indignant, there may be a reason. The more eyes on a car, the better chance to spot a problem.

Q. What can you inspect yourself?

A. Mechanical noises, pulling in the steering, body gaps, paint condition, etc.

Q. What kind of documentation is necessary? Do you recommend completing a bill of sale?

A. I try to always produce a bill of sale that states the vehicle identification number, make, model, mileage, selling price and any agreements that have been discussed between the buyer and myself. I have bought many cars without the bill of sale though. Overall, I would recommend a purchase agreement, typed and to the point, signed by both parties, with a copy to each person.

Q. Can you share any negotiating tips?

A. I always bring the total amount that I am willing to pay for the car. In one pocket I keep my first offer in cash. In other words, if the seller is asking $7,000, I bring $5,800 in my left pocket, and maybe another $500 in the other pocket. Flashing cash while making an offer can help immensely! Whenever making a large cash transaction, I always bring at least one other person with me (preferably someone big). Also, always be prepared to walk away. Then, call back the next day, and the next day. You never know when you’ll catch someone in a desperate state of mind. Remember that there are other cars out there, even though this one sounds perfect.

Q. How can you be protected from scams?

A. Well, there are a few different scams that I know of. Cars that have been previously damaged being sold as good cars, cars that have had the miles turned back, cars that are stolen and retagged with different VINs, and online sellers that ask for a deposit before you see the car. All of these are avoidable with proper inspections and common sense. Common sense should tell you don’t pay someone for a car you haven’t seen! (I’ve seen it happen.) Rule of thumb: If it seems too good to be true, it probably is.

Q. How do you know the car's value? Do you recommend using a service like Kelley Blue Book?

A. Kbb.com and nada.com aren’t really that accurate. Personally, I look through Craigslist.org and the local paper to see what the car that I am looking at is generally selling for in my area. I always take about 20 percent off of the asking price to project a true selling price.

One final tip: Call a random car dealer and give them a description of the car you are looking to purchase and ask for a trade-in value on that car. Whatever the number, remember, that is what your potential seller could get for the car by trading it in. This number is usually really low, but people get lazy and trade cars in all the time. Work up from there to formulate your first bid.

Angie Fisher is a former associate editor at shopautoweek.com. Angie loves anything Audi—of course, if she had to pick it would be the R8. Realistically, though, right now she is looking at a Jeep Wrangler. She graduated from Central Michigan University with a bachelor’s degree in journalism and is the recipient of a Michigan Press Association award. Angie is married and loves spending time with her dog. Follow her on Twitter @Ang_Fisher.