Hello there. I've been buying, and selling Diecast on ebay for a while now, and just as with any other item you can find on this huge site, there are a few points worth thinking about. This is not intended to be an absolute guide, but as I've had a little experience now, I thought it might be worth passing some of it on ...
Where to place your item.
Diecast collectors come from many camps. There are those who collect a particular theme, or scale, or manufacturer, and there are those who like a certain era or make of model. In short, it's hard to know when selling just who your customer would be, and so which catagory to place your listing. If you have a known manufacturer, such as Dinky or Corgi, thats shown in the choices when you go to list, stick with that. Some popular makes will have sub catagories such as 'car' or 'commercial'. Naturally a car is a car, but if it has the logo's of a company on it, it would be best to place it in the commercial listings. there are generally more collectors of commercial vehicles, and so you have more chance of getting bids. Placing it in the 'other' catagory is pretty much a no no, as this is just a general anything else area, and is unlikely to get as much attention.
What To Mention In The Listing.
Most old Diecasts will have picked up the odd scratch or scrape, most were toys after all, and the general term used for these models is 'playworn'. There is a huge market for most discontinued models in whatever condition, and collectors are very particular about the models they obtain, and you really need to mention anything worse, such as a bent or damaged fender, or any dents. Missing parts should also be mentioned. I know it's not always possible to know if there should be more to a model, but if it only has one headlight, or holes on the roof, it's not rocket science to realize that there should be more to it.
As with any item, a picture can speak a thousand words. The best way to show off your item is to have two pictures, which between them show all four corners of the item. I have often seen folks put up two pictures, both of the same side but from different angles, and my first thought is what are they hiding on the other side. Also, try and make your pictures as light as possible, especially if you are selling a 'playworn' item. I tend to use natural light in all my pictures as I find it works for me, other sellers I know use light tents or mirrors under the model to boost the available light. You may think showing the faded or chipped paint off putting, but a collector will accept this. What a collector won't accept is a siloette of the model with just a hint of it's colour. I've picked up many a bargain from these 'guess the model' pictures, but the seller has lost out, and paid extra to put the loss making picture in.
Diecast collectors can be very generous buyers, and will pay what seems very good money for an old toy, but if you really want them to pick your particular old toy, make sure you have covered all the bases. By this I mean, make it clear that you offer reduced postage for multiple wins. I personally always look for this, as a diecast model doesn't take up to much room in a package, and if a seller is selling something I want and offering reduced postage, I'll check the rest of the listings they have, and sometimes buy items I normally wouldn't on their own as a result. Fair postage is another must, and Paypal, love it or hate it, is a great attraction in a collecting area where many buy and sell. Lastly, offer to sell worldwide. There has been some debate about the closeing of visibility to the USA market, but diecast collecting is a truley international hobby, and an average 50% of my sales end up going abroad.
At the end of the day, dealing in diecast on eBay can be a lot of fun and very profitable. It is a large market and has a good honest and regular international set of buyers. Your old toys from the loft could honestly surprise you. I hope these few brief pointers have been of help.