Get the Documents ready
Put together your service and emission inspection records, the title, and the paperwork required to transfer ownership (you can download from your state's DMV site).
Run a Vehicle Report
Run a vehicle history report on AutoCheck.com or Carfax.com ($30-40), and post it with your ad (see below) will nail you higher prices.
Do Some Light Fix Ups
Maybe it's worth to do a window wash and interior cleaning, but don't bother with a car detailing that costs $100. For any major repairs needed, factor that in your price. You can offer to take the car to a mechanic for a check if the buyer asks and pays for it. Or you can make the used car available for a 3-rd party inspection, such as AiM Mobile Inspection.
Put up for Sale at Multiple Sites
You can post free ads on Craigslist and Cars.com, but to pay $25 - $125, you can put up for sale at Cars.com, AutoTrader.com, eBay Motors with more photos and longer ad running time. Like selling anything else, if you can create a story and explain well why you are selling the car, you can get higher price for your item.
Get Cash or Money Order
Never meet with the buyer at your home, meet at a public place. Never let the car out of your sight, unless you get the money - cash or money order!