I recently purchased a new vehicle; a model that I've wanted for several years but could never afford until recently. I finally decided to buy used (2 to 3 years old as that seems to be the sweet spot with depreciation) and did all sorts of research about negotiation. I went ahead and got outside financing pre-approved so I'd have a baseline rate the dealership would have to compete with.
While researching, I found that you can sometimes get a good deal on 'leftovers'. For example in the US, the 2015 models will be out in the next few months. There are still a few brand new 2013 models sitting on the lots. I looked and found only one left in my area.
So I picked out several used 2013 models with less than 10k miles on the odometer, went down to the dealership, and asked them to convince me why I should buy their nearly two year old "new" car, when I could pick up the same year model slightly used for many thousands less.
I had already consigned myself to buying used, and already had the financing, so it wasn't difficult to get up and start walking out when they initially wouldn't come down in price. But they were bluffing, and they needed to move the car. They knew I wasn't bluffing. I was ready to go buy one of the used cars I had picked out. So they came down in price, and I got the car below invoice, and almost 8k below sticker price (on a car with no incentives that often retails several thousand above MSRP). That beautiful new car turns into a lead weight if it sits on their lot long enough.
If you do your research and have a good poker face, you can find a good deal on a car. I've been royally screwed in the past, largely because I didn't understand how car buying works and didn't take the time to research. (Hint: When the salesmen give each other a high five on your way back from the finance office, you've been bent over the fence.) Now I know (a little) better.