I've sold the three cars in my sig privately. The biggest pointer I can give is to get some fantastic pictures of your car done. This can be the difference between someone browsing past your ad or clicking on it. With regard to pictures, get one from all four corners, the engine bay, interior, a close up of at least one of the wheels and maybe even a pic of all the cars documents and receipts. Make sure the car is immaculate when you take the pictures and when they come to view.
When people call be polite, accomadating and flexible. If there are any issues with the car tell people, even volunteer the info before they ask. For example, if the rims need a refurb, tell them before they come. They then won't come and be dissapointed by the condition. Also, if there are any issues such as this, show that you have a resolution in place e.g someone who will refurb the wheels for the buyer or that you will do it before they pick up the car etc. The point of this is to avoid any negative conversations. You want to be talking about only positives. One 'trick' is get them to sit in the drivers seat, you in the passenger seat, talk them through the interior gadgets etc and then get them to start her up. The engine note will get them instantly, they will no longer be listening to you but hearing that V6 growl Take them out in it too. Obviously you need to be wary of people, lock your front door and have someone in the house to phone the police or come out with a bat if needed.
Depending on how quick you wanna get shot, I always put my car up for sale at whatever the dealers are selling theirs for. This gives you room to reduce it accordingly. Make your ad a real long detailed description of the car. Make it sound like the car has had no expense spared and that they are getting a bargain. Assume that everyone who reads the ad is an idiot. List every conceivable feature, not all people are car geeks like us lot. Specify the difference between your 07 car to an 06 for example.
One under rated source for selling cars is eBay. I sold both my zeds to people on ebay. Be prepared for jokers wanting to buy your car for peanuts. A lot of traders use eBay to buy cars that are underpriced. I got loads of offers AFTER the auctions had ended from people hoping that the car hadn't sold and I was desperate to get rid.
If I was you I'd stick it up for £22,995 and then systematically reduce it by say £1000 every 2/3 weeks or so. I suppose if you have finance or a loan out for the car then you have to consider the monthly payments while you still have the car.
Lastly, don't panic! The car market is very very slow at the moment as the credit crunch bites. The car will sell, how much for will depend on how you apply any of the above.
Hope this helps
This must be my longest post for about 2 years, I'm going for a nap