A classic car can be sold whole, or for parts. If the car is not running, and probably will not run without a large investment in time and money, it will be very hard to sell whole. You will get less money if you sell for parts, but it may help out other classic car owners looking for hard-to-find parts for their cars. You may wish to sell the parts individually yourself, but it is easier to sell the entire car to a specialty parts dealer.
If you intend to sell the whole car in working order, detail the entire car. Clean the interior, clean heavy grime from the engine parts, and thoroughly wash and wax the exterior. Make sure tires are clean and properly inflated (especially if the car is used infrequently). Take photos of the car after it has been waxed, preferably in strong sunlight so that it gleams. Be sure to take close-up photos of any distinctive features that make your classic car special. If they are well-maintained, they will be selling points.
Fix any small problems you can yourself, and itemize a list of any major work that needs to be done. Account for needed repairs in your asking price, and disclose the list to potential any buyers.