The first thing you need to do is call the auto salvage companies in your area. Ask them how much they pay for junk cars. Scrap metal usually sells by the pound. Most cars have a sticker in the drivers' door that tells the weight of the vehicle. By reading this you can get an idea of how much cash you will get for your junk car.
When you contact the salvage yard, ask them what they require as far as buying a junk car. Many places ask that you remove the wheels and tires before bringing them in. They sometimes require that the gas tanks have been removed as well. Some will accept them without the removal of wheels and tires, but you will receive a less amount for your vehicle.
You need to find out if they will pick the car up or if you need to bring it in. Depending on your area they may be willing to pick it up, but most often they will pay more if you bring your junk car to them. You should only have the car towed if it is not in drivable condition. If you do have to tow your junk car be sure to check on the towing laws in your town, you do not want to get a ticket.
Before you commit to any action, you should always call several salvage yards and get price quotes before deciding on a specific yard. You want to sell your car to the one that pays the most. Keep in mind that the price of scrap metal fluctuates. It may sell high today and be considerably less tomorrow.
Finally, if you hold any entrepreneur values, scrap metal can be a very beneficial business. If you know anybody who is trying get rid of their junk cars, you can actually buy it from them for cheap, and re-sell it to the junk yard and make a profit off of it.