Don't waste your time with back street car auctions - go for the big boys like BCA and NCA. British Car Auctions (formerly ADT) is the biggest car auction chain in the country, and National Car Auctions is next in line. I've bought cars at both of these, as well as back street auctions, and have gained from the experience. Let's run through a few points.

These are the places where you find very few modern cars, they're mainly bangers at least five years old entered by individuals who have bought them cheap with a view to re-selling at auction. Cars get sold for as little as a hundred pounds but rarely for more than a couple of thousand. You will find lots of very smart looking old cars because they have been re-sprayed specially for the auction. In fact that is probably all that's been done to them since they were bought in the very recent past for a fraction of the reserve price. The place is usually full of dodgy looking characters who are likely to push up the bidding. It's common to see the same car go through three times in the same session - the original owner ended up buying it first time whilst attempting to push the bids. Third time round it will be sold or withdrawn because if the owner wins the bidding this time he will have to pay the commission. The bidding is often slow, trying to pump the last fiver out of every sale, and this slows the auction down considerably.

These are professionally run outfits with the majority of cars being entered by the main dealers (many of their part exchanges end up here), lease hire companies (rarely more than 3 years old) and the manufacturers, like Ford, who run schemes for the disabled such as Motorbility (all cars are sold after 3 years). These are the places that the car dealers buy their stock from. Remember that the dealers have to add on a profit so you can out-bid them and still buy it a lot cheaper than you would from them. If you look around you will see mostly respectable looking businessmen. There is seldom any jiggery-pokery and faults are often declared. If you are buying a car for over £3000 then you are usually in safe territory. They do have occasional bangers, but they are seldom done up and usually go for a song. The bidding is usually quick and eficient and the cars are sold without delay.

Get a catalogue and look the cars over well before the sale, identify the one's you are interested in and try to be there when they are started up for the first time - you can learn a lot more from a cold engine than from a warm one. Watch the auction to see what similar vehicles are fetching and be sure to check the value in Parker's or a similar publication. Make allowances for mileage and general condition and set a maximum price you will pay. Do not exceed your maximum under any circumstances, take a friend with you to enforce that discipline - there will be plenty more to come. The more flexible you are in your choice of car, the more likely you are to pick up a bargain. If there are superficial scratches in the paintwork the dealers will be less interested and will drop out of the bidding much earlier.

On top of the price you bid for a car, there will be an additional charge for "title guarrantee" which is an insurance that will refund the purchase price if the car turns out to have been sold illegally. It varies in price but is likely to be over £100 and probably compulsory. It means you have peace of mind. Happy hunting.