Renting a car is a potential minefield — there are so many ways in which you can be ripped off, misled or overcharged. But you can come through it all unscathed if you know the tricks of the trade and how to avoid them. Here’s our cut- out-and-keep guide to car-hire scams and how to avoid them.

The scams

SCAM 1: THE EXCESS CHARGE

Most companies claim to offer “fully inclusive” or “drive-away” prices. Don’t believe a word of it. Although their prices include collision damage waiver — which limits your liability in the event of damage or theft — you’ll still pay a hefty excess. Excess charges can be as high as £4,000. You’d be forgiven for failing to notice the size of the excess when you book because it’s usually hidden in the small print.

But when you pick up your car, staff may point it out. They’ll then offer to sell you extra cover. This extra cover — Super CDW — will reduce your liability to zero. It’s worth having, but expensive — as much as £15 a day, or £210 for a fortnight.

How to avoid it: you don’t need to pay exorbitant prices for SCDW. Instead, insure yourself against excess charges with Insurance4carhire.com. It charges £51 a year within Europe, £125 worldwide. Or book through a broker such as Holiday Autos (0870 400 0012, www.holidayautos.co.uk) or Carrentals.co.uk (0845 225 0845, www.carrentals.co.uk). Both firms offer excess insurance at £2.50 a day.

SCAM 2: THE EXCLUSIONS

Many drivers are surprised to learn that their insurance doesn’t cover windscreen, wheels, tyres, roof or undercarriage. Rental companies say this is because a typical prang involves dents and scratches to doors, wings, bonnets and bumpers. So if you’ve damaged the roof or the undercarriage, you must have been abusing the vehicle — driving off road, perhaps. This means that you’ll still be billed if you suffer a puncture or a chipped windscreen. Some idiot slashes your tyres? You pay. Repair bills can be extortionate. Peter Jackson, who lives in Turkey, returned a car at Stansted with a windscreen chip and was charged £617. When he complained, this was reduced to £300.

How to avoid it: even the most cautious driver can get a puncture, so protect yourself. The annual policy offered by Insurance4carhire.com covers tyres, windows, roof and undercarriage. The £2.50 a day policies from Holiday Autos and Carrentals.co.uk do not.

SCAM 3: WATCH WHAT YOU SIGN

When you arrive at an airport pick-up desk feeling tired, stressed and anxious to get to your final destination, you’re at your most vulnerable. A cynical company might think this is just the time to hit you with the hard-sell treatment. One popular scam is for staff to offer SCDW, saying, “It only costs €12.” You scribble your initials, not realising it’s €12 per day.

The problem appears to be worse in America. Patrick Sheehy of Haverhill, Suffolk, arrived in Tampa and declined the £14 a day insurance, which he didn’t need. A clerk told him: “I know you’re in a hurry, so just sign by the crosses and away you go.” Only on his return did Sheehy find he’d “agreed” to pay £196. When he complained, the staff shrugged and said: “You signed. That’s it.”

How to avoid it: read and understand your travel and home-insurance policies to ensure you don’t buy duplicate cover. Get a printout of the rental company’s terms. On collecting your vehicle, don’t sign anything you haven’t read and understood. Remember that every time you scribble your initials in a box, you may be agreeing to pay for an extra you neither want nor need: personal insurance, rip-off petrol refills, personal-effects cover, or Super CDW. Make them explain each one.

SCAM 4: THE PETROL RIP-OFF

Buying petrol from a car-hire company can be costly. A reputable firm should give you three choices: to drive the car away full and return it full; to buy a full tank and return it empty; or to pay only for what you use.

The first is the simplest, but you must fill the tank to the brim — if staff can squeeze in a few more litres, they may hit you with a “refuelling charge” of up to £45. The second option is expensive. You’ll pay up to 40% more than pump prices and you won’t get a refund on the fuel you don’t use. If it’s difficult to return a car with a full tank, it’s almost impossible to do so with an empty one. The third option might look attractive until you discover what you’re being charged for the petrol you’ve used — sometimes more than double the pump prices.

How to avoid it: some rental staff claim you must take a full tank and return it empty. To avoid being bullied, check the terms when you book and keep a copy with you. Refill on the journey back to the airport and keep receipts.

SCAM 5: DENTS AND DINGS

It’s a familiar story. You collect your car from a badly lit basement car park, drive it sensibly and return it undamaged, only for staff to give it a quick inspection and find a tiny scratch or dent. The first you know of it is when a charge for “damage” appears on your credit-card bill.

How to avoid it: if you don’t have a policy covering excess payments, you ought to assume you’re going to be ripped off, so do everything possible to stop it happening. Inspect the car thoroughly on collection and ensure any damage — however minor — is marked on the vehicle-condition report. Ask staff to drive the car into a well-lit area before you inspect it. Take before and after photographs of the car (if you have a digital camera, switch on the time and date display). On return, wait while staff inspect it, then ask for a copy of the final report. If nobody inspects the car, write on both copies: “Staff declined to inspect vehicle.”

Fight back

Be meticulous, both at collection and drop-off. Leave time to read the small print and insist on vehicle checks. If a car-rental office will be closed when you plan to drop off, consider using an alternative company. And, most importantly, if you think you’ve been ripped off, complain. Armed with evidence, you have a good chance of getting a result. Many Sunday Times readers have reported successful outcomes dealing with UK-based customer-services teams. If you booked your car through a travel agent or broker, ask them to help.

Peter Woodrow of Raglan, Monmouthshire, rented a car from Avis in Eilat and was charged £185 for a windscreen chip. He wrote to Avis. “The initial response was that they could not intervene, as the company in Israel was a franchise, but after months of protracted correspondence, it was refunded.”

Acronym buster

CDW (collision damage waiver) reduces your liability in the event of an accident. Without it, you could face a bill equal to the replacement cost of the vehicle.

TW (theft waiver) is the equivalent of CDW, but protects against theft. Also known as TP (theft protection).

SCDW (Super CDW) does the job that CDW ought to do, reducing your liability to zero. Often sold in conjunction with Super TW.

PI (personal insurance) pays out if you kill or maim yourself or a passenger. Usually covered on regular travel insurance.

PEC (personal effects cover) pays out if your property is stolen from a vehicle. Usually covered on house insurance.

Times recommends

• Oasis of the Seas: the Times review
• The 20 best new year party places to stay
• Green Spaces 2009: are you the winning writer?