That's often very tricky. When I think of the Internet and all its hyped promise, I often am reminded of the story about the emperor and his clothes. It may not be fair to call the Net naked, but let's just say it's having trouble hiding all its private parts. If using the Internet doesn't sound like you, a new car broker might. Just remember that using a broker to act as an intermediary comes at a price.
Some brokers also help with financing, trade-ins, all the paperwork and so on.
The safest ones to deal with hold a dealer licence that requires them to conform to the standards of car dealers. Make sure the selling dealer's name appears on the title and the cheque for final payment. Don't do the entire transaction through the broker. You, the buyer, could end up being listed as the second owner of the vehicle, thus compromising your ability to get warranty work performed or to qualify for special factory adjustments. If a problem arises over and above the normal warranty, the chances of getting that through a dealer you didn't buy the car from are slim.