The way cabin air is circulated makes the plane a prime breeding ground for colds and flu viruses.

True: A qualified yes because there's no scientific proof that breathing someone else's air in the cabin will make you ill. It's true that some airlines save money by recirculating air instead of purging and replacing it, so Greenberg's advice: Hydrate yourself while on the plane, wash your hands often, and turn off the air vent over your head to not only avoid a stiff neck but also keep your own air around you longer and put off breathing someone else's.

Your plastic hotel key card can be used to steal your identity and credit card account information.

False: Simply put, hotels do not put your personal information on the card. At the most, they will encode the room number and activation date.

Back up your files because X-ray machines at security checkpoints can erase the hard drive on your laptop.

False: X-rays are a form of electromagnetic energy, but they're not magnetically charged. Electromagnetic energy is basically like light, and can expose your camera film just as light can, so watch out for that if you're one of the few photographers still using film. But sending your laptop through the X-ray machine won't damage it. There is something to be careful of, however. In the unlikely event that the security people let you take your laptop through a metal detector or examine it with a metal wand, you're at risk. These detectors send out a strong magnetic pulse that can erase hard drives.

If you use your Blackberry or cellphone in flight, the plane will crash.

False: The FAA has tested all sorts of electronic devices for 25 years, at 100 times the RF interference levels—and nothing happened. The FAA simply states that no link between operating the devices has been proved. It's been left up to the airlines to determine their own policy—and that policy is to put away your Blackberry. By using your cellphone during flight, you risk interfering with a flight crew—but the plane won't crash.

"All-inclusive" cruise means you can put your wallet away for a week.

False: It used to be true, but no longer. Cruise ships now charge for any number of things, including a fee for unlimited soda. A new rule of thumb for budgeting your next cruise: Take the basic cruise fare and multiply it by 1.75 per person.

Your personal auto insurance covers damages to your rental in case of accident. If you don't have your own insurance, your credit card will cover you.

True: Unsuspecting renters who don't own a car—and thus don't have their own insurance—think they are covered by their credit card. Not so. Almost all credit card companies offer something called "secondary insurance," which only kicks in when you've exhausted all the limits of your primary policy. And if you don't have a primary policy, then you are not covered at all. But even if you are covered, check your policy limits. If your personal car is only worth $5,000 and you total a car worth $20,000, you're out $15,000.

To save money in Europe, trains are the way to go.

False: European trains are no longer economical alternatives to air travel. Low-cost European airlines are now cheaper than intra-European train travel. On Ryanair, an off-season round-trip flight from Rome to Frankfurt can be as low as $90. By comparison, a point-to-point train ticket from Rome to Frankfurt starts at $326 each way and takes about 12 hours of travel time.