Call all around, often. I found a used TDI NB at a VW dealer just by asking the salesman I had bought the new tdi Golf from a week before. They had just got it in the night before. It wasn't listed or posted anywhere, and I snarfed it right up.In this case it was VW certified, so that meant they had verified all the maintenance, they knew it wasn't a lemon, and they gave me a 2 year/24k mile warranty on all mechanical systems.It was also $500 cheaper than a similar used TDI NB on the lot at a Chevy dealer just down the road.Very happy with the deal.