"Buy on the rumor, sell on the news," they say. (Who is "they," anyway? I once heard that it's the Dick Van Patten family.)

If you've been thinking of investing in credit- and charge-card companies such as American Express (NYSE:AXP), JP Morgan Chase (NYSE:JPM), Morgan Stanley (NYSE:MWD), Capital One (NYSE:COF), or Bank of America (NYSE:BAC), and you're an investor who follows adages, you might be looking for some rumors. Here are some that have been circulating around the Internet. I'm also including the bottom line on each, from Snopes.com.

Let's start with an amusing one. Rumor: "Eelskin wallets demagnetize credit cards due to leftover charges from the electric eels used to make them." The bottom line? It's false. What might actually be causing a problem is the magnetic clasp found on many eelskin wallets. Sorry, eels.

Next up: "Thieves are using camera cell phones to capture credit card information." Snopes won't say whether this is true or false, but it's certainly possible. It doesn't hurt for us all to be a little more aware of those with cell phones around us, as now they can be capturing photos. Perhaps keep your card a little more concealed in your hand when you're out and about with it -- or at least brush your hair and smile.

Here's something that's more a scam than a rumor. It's worth learning about, though: "Con artists gather marks' banking information by promising $200 Wal-Mart (NYSE:WMT) shopping sprees in return for $3.49 processing charges." Snopes reports that this is a real fraud, costing many victims several hundred dollars. If you don't think you'd fall for it, think again. You're called and informed that to celebrate its 50th anniversary, Wal-Mart is giving away some shopping sprees and you've been selected. To receive a packet of vouchers worth $200, just pay $3.49 (via credit card or bank payment). (Note that the company was founded in 1962.) Many people will think it's worth a shot. The truth, though, is that more often than not, if something sounds too good to be true, it is.

Let's hop over to Washington, D.C. now, shall we? Apparently, "71 [congressional representatives] have credit reports so bad they can't qualify for a credit card." Snopes is right on when it responds: "Heck, a single late payment can ruin your credit report these days, assuming your spotless rating hasn't already been done in by completely erroneous information mistakenly placed on your record by a credit reporting agency." We've reported on this scary state of affairs many times.

My own bottom line is that you should be ready to question most emails that cross your screen. There are a lot of hypesters and fraudsters out there, eager to make your life miserable. (Learn about the scary practice of "phishing," for example.) Identity theft is just one of many headaches that you'd do well to learn to prevent.

Learn much more about the surprisingly interesting credit card industry in our Credit Center, which also features tips on getting out of debt, along with guidance on how to manage your credit effectively. (We even offer spiffy Motley Fool credit cards.) Really. I mean it. There's some great stuff in our Credit Center, and it's all free reading.

The following articles can help you:

You can also read about all things credit-related on our Consumer Credit/Credit Cards discussion board.

Longtime Fool contributor Selena Maranjian owns shares of Wal-Mart. The Fool has a strict disclosure policy.