1. Make it appear as attractive as possible
Let's say you were to go on a date with the man/woman of your dreams. Are you going to wear just any old outfit and not even go to the trouble of brushing your teeth and hair? Probably not.
The same goes for your car. In order to look attractive to potential buyers, it will need some TLC such as a proper clean (even better, a professional valet) inside and out. And don't forget the engine bay. When that buyer lifts the bonnet and lays his eyes on a grimy engine bay, he won't buy, despite the exterior looking like a million dollars. Watch how to do this here.
How do you know what your car is worth? Use AutoTrader's free valuation tool here.
2. Take good photographs
Just think how many other people out there are advertising their cars in the classified section of AutoTrader... you want yours to stand out, right? And don't forget that less isn't more. You need to be the potential buyer's eyes. Also take photos of the engine bay, the tyres, the dashboard, the boot, rear and front seats...basically everything you would like to see if you were the buyer. Click here to read How to take pictures that sell your car fast.
3. Do minor repairs if needed (or have major ones done by the pros)
If your car has dents and scratches, take care of it! Even if it costs you a few bucks, it's still a big investment. If your car looks well looked after, it doesn't allow the potential client too much of an opportunity to haggle down the price. If you had anything repaired or replaced, remember to keep proof thereof.
Recommended reading: How to get your car ready for a private viewing.
Also read How to negotiate when selling your car privately.