Steer clear of ex-rental cars.
Things are not always as they seem. Punch the right words into an internet search engine and you'll soon discover cases of people who've purchased what they thought was their daily bread, only to discover that the loaf in question was really a mouse coffin with poppy seeds.
Others have attempted to buy tinned soup, finding afterwards that what they really had was a chicken-and-corn-flavoured razor-blade storage device.
But for sheer numbers of next-day nasty surprises, nothing beats the used car.
Get your choice checked by a licensed mechanic.
Used, second-hand, pre-loved; call it what you like: the fact remains that many unwitting consumers think they're buying a new set of wheels but end up with a dog. (Which is massively unfair to dogs, who I've always found to be generally affable and mostly friendly, and hardly ever require the services of a motoring-club breakdown van to move them off the driveway).
It's often said that sharks can smell blood in the water for kilometres, but those aquatic killing machines have nothing on some of the people - professional and amateur - who sell used cars. (Again, I suspect this is an affront to the animal kingdom.)
So, if they (the sellers of dodgy second-hand cars) are out to get you (the hapless used-car buyer), what can you do? How do you spot the sharks and the dogs?
Look for accident damage and repairs.
Glad you asked, because here's the nitty-gritty of not getting caught with a hound in the garage or losing an arm and a leg in the process.
Weight for age
Let's start with a simple one.
Many a used-car advert contains the phrase ''60,000 kilometres on the odometer''. This may well be true, but it doesn't account for the fact that the car itself covered 200,000 kilometres before that particular odometer was fitted.
Plenty of cars sport replacement dashboards and, as well as the obvious question of whether the mileage showing represents the car's entire life, you also need to ask the question: How big was the shunt that required a new dashboard to be fitted?
Older cars are also ripe for what's known in the trade as a ''haircut'', in which the odometer is simply wound back (usually with a power drill on the speedometer cable). While digital speedos on new cars have solved that problem, the replacement dash is still rife.
So your job is to figure out whether the mileage showing is fact or fiction.
A car with, say, 60,000 kilometres showing should not have holes in the carpet under the driver's heel, nor should the pedal rubbers be worn smooth. The driver's seat shouldn't be sagging and the writing shouldn't have worn off the switches and dials. Why is the service handbook missing? Walk, brother.
Cheap and cheerful. And trashed.
Plenty of people buying a used car are doing so because it's a cheaper option. So cheap, cheerful cars are often in their sights.
Fair enough, but it pays to remember that fleet buyers were attracted to the same makes and models back when they were brand-new. And don't be fooled by the car being presented as a private sale; it could be on its third owner or the seller could be the fleet manager's brother-in-law working on a percentage. (See ''Who's the real seller?'')
Either way, your job is to make sure you don't unwittingly purchase a car that spent the first three years of its life being thrashed by a succession of spotty emos delivering Friday-night Chinese takeaway while listening to chill-out ballads on their iPods.
Luckily, there are some classic giveaways that this may have been the case.
A large car with holes drilled in the dashboard (for radios and despatchers) was probably once a taxi or hotel limo. A small car with the same markings was probably a security officer's transport and flogged mercilessly from midnight to dawn for those same three years in the hands of a frustrated security guard.
A car with a discoloured passenger's seat and a lingering scent of Meat Lover's was, you guessed it, once a pizza delivery car driven by crazed teenagers with ashen faces and eyebrow piercings who thought the best way to retaliate against $8.50 an hour was to systematically destroy the car they were given to drive. Payback's a bitch.
A close look at the car in strong sunlight may also reveal shadows on the paint where corporate decals once resided.
And airline decals on the rear window? A former rent-a-car, to be sure.
Crash, bang, wallet
Crashes are a fact of life, but you still wouldn't want to be saddled with a car that has been seriously pranged and fixed on the cheap.
The golden rule with crash repairs is that if you can see evidence of them, then they haven't been done properly. So check the paint for colour matches, as many insurance companies will insist repairers blend new paint into old rather than repaint whole sections of the car. It's cheaper that way.
Check the window rubbers and under the wheel arches for signs of overspray, as this suggests a quick patch-up job rather than a proper repair.
And here's one of which you mightn't have thought: Have a look at the condition of the car's number plates. Even if the crash damage on the car itself has been repaired invisibly, nobody thinks to replace the number plate, even if it's slightly bent or scuffed from the prang. It's a dead giveaway.
Sometimes an older car won't try to hide its past at all and will be presented for sale with body panels that have obviously come from a donor car. A white car with one green door seems to be the prevalent colour scheme.
The question you must grapple with is this: Was this a white car that had a small crash, or a green one that has been in a monster?
Who's the real seller?
A bit trickier, this one, but it's important because it can suggest a car that has been difficult to sell up to now (for a variety of reasons, none of them good for you).
What you're trying to spot is a car that is being presented as a private sale, but is in reality stock from a used-car yard that is proving impossible to shift.
In such cases, a used-car dealer may try to flog the thing from his cousin's driveway (known in the trade as the back door). This offers the seller the opportunity to play dumb re the car's actual condition and conveniently removes the obligation to provide the statutory warranty that would apply if the car was sold off the forecourt.
We'd also place in this basket the person who buys and sells cars for profit, even though they're not a licensed used-car dealer.
Either way, it is not cricket and the car in question may not be quite what it seems.
Fortunately for you, the seller's greed can be their undoing, as they're likely to be selling multiple cars this way at any one time.
So, when you phone up to make your preliminary inquiries, don't ask about ''the blue '86 Commodore SL''; instead, ask about ''the car in the advert''.
If your opening gambit is met with ''Which one?'' you could be on to a back-door dealer.
The same goes for the actual inspection, especially if the seller's front yard is full of cars.
Be wary of alleged private sellers who have those big, bold ''$4999'' signs displayed on the car's windscreen, too. Where - other than a used-car yard - did they get hold of that?
Also be wary of sellers claiming to be out at the local cafe or going for a walk; you want to see them open the door to the house to make sure they actually live there (or know someone who does).
If you're spending a decent amount of cash on a used car, an independent inspection is a heck of a good way to ensure you don't get dudded.
Honest sellers will not have a problem with this taking place before the purchase, especially since the buyer (that's you) bears the cost of any such inspection.
It can be assumed, then, that any seller unwilling to allow this process to take place is either hiding something or is a dill. Either way, you don't want their car.
Your own check should include the service record.
Why buy a car with an incomplete service history when there'll be another one along in a minute that does have one?
This is especially important in something such as a relatively new Hyundai, where a portion of the five-year new-car warranty might still apply. But it will only do so if the service record is complete.
Oh, and don't be sucker-punched by Mitsubishi's 10-year warranty on its cars' drivetrains: The 10-year cover only applies to the first owner and isn't transferable to subsequent keepers.
A sticker for detail
For reasons known only to their lazy selves, most people can't be bothered removing their personal touches from a car before they sell it.
The nodding dog and air-freshener on the mirror are easy enough to get rid of, but the decals on a particular car can be a mine of information.
Anything with an R.M. Williams or Bundaberg Rum or a Southern Cross decal (even if it's not a ute) has probably been to hell (or worse, Deniliquin) and back at the hands of a redneck apprentice who thinks preventative maintenance is for wimps.
The other one to watch out for is the car covered in decals from surfboard and wetsuit companies. Yep, the car is a fair bet to have spent hours - if not whole days - parked at the beach while its waxhead owner cuts sick on the gnarly sets and winds up stoked. The car, meanwhile, eventually winds up full of rust holes.
Any car with a tow bar (where there's also a boat parked in the front yard) has almost certainly been submerged to the back door handles at least once in a ham-fisted attempt to launch the tinny.
But if this lot hasn't put you completely off the idea of a second-hand car, good for you. The world needs optimists.