This may seem obvious but the better condition your vehicle is in, the better the price you will receive. Simple!
Clean your car - Get out your bucket and sponge and give your car a good clean inside and out. Straight away its more appealing to a potential buyer.
Service records - Ensure you have all the service history and MOT information available. This really helps the value of any car, especially if it has been cared for by the manufacturer. An up to date MOT of course is essential.
Check everything works - Take a few minutes to ensure all the electrics are working correctly; lights, windows, washers etc. If not, its a good idea to get those looked at prior to sale, otherwise it will effect the sales price.
Minor damage - If your car shows signs of minor damage, such as a scratch or dent, you might want get that repaired.
Spare keys - Sourcing spare keys can be another cost to the potential buyer, so have a good look around and ensure you have 2 or more keys for the vehicle.