Consumers are paying close attention to all aspects of their finances these days. Plunging investments. Falling home values. And, erroneous credit card charges. When the latter are discovered, many consumers file disputes with their card issuers.

No industry statistics are available about how often such disputes are won by consumers. But to maximize their chances, consumers should know how to navigate the maze of rules governing credit card disputes.

Under federal law, "You're entitled to an investigation (of the dispute) but not entitled to a particular result," says Chi Chi Wu, staff attorney at the National Consumer Law Center.

Mike Gaynor of Chicago says he's become an unwilling expert after spending almost 10 months and more than 100 hours fighting credit card charges.

In May, Gaynor, 44, and his wife, Kerry, 39, filed a dispute with Citibank for $130,000 — an amount that has since been revised to $46,000 — after he failed to get rugs, couches and design services purchased from an interior designer. Some of the furnishings were delivered after he filed the dispute, but Gaynor said he took Citibank's advice and refused them because their delivery was extremely late. He had already bought other furnishings.

The dispute dragged on for months before MasterCard stepped in. MasterCard decided in favor of the merchant, his bank told him in a letter, because he refused delivery of the order.

Gaynor says Citibank is working with him to locate some furnishings and is considering giving him a credit for others. But that, while helpful, won't dispel his anger.

MasterCard declined comment on the consumer's case. Generally, the card association steps in only when banks can't resolve the matter and never has "preferences in the outcome," says Chris Monteiro, a MasterCard spokesman.

Citibank spokesman Samuel Wang said the bank is "working with these customers … toward a complete resolution."

Whether the issuer decides in favor of the bank or the consumer depends on whether it's a valid claim and what type of documentation each side has, says Nessa Feddis, a vice president at the American Bankers Association, a trade group.

While it's not always possible to avoid credit card disputes, here are some tips for dealing with them:

•Get promises in writing. Save receipts. For big-ticket items, also ask for written confirmation of when the item will be delivered and what services are provided as part of the purchase.

•Know the rules. The Fair Credit Billing Act gives consumers the right to dispute a credit card purchase or withhold payment for a card purchase — but only under certain conditions.

Disputes must generally be filed in writing within 60 days after the bill is sent. In certain disputes, the goods or services must cost more than $50, and the transaction must have occurred in the purchaser's home state or within 100 miles of his or her mailing address. Although state laws vary, items bought online or by phone are generally considered purchases made where you are, Feddis says.

While disputing a charge, the card holder will not have to pay the contested amount and won't incur interest on it. If the dispute is lost, the card company is allowed to charge interest back to the date you filed the dispute, after a standard grace period.

•File the dispute carefully. Banks classify card holders' disputes into nearly two dozen categories, such as "merchandise not received" or "canceled recurring transaction." But generally, if filed as an "unauthorized transaction" — as long as it is unauthorized — you'll have more protection.

By law, liability for unauthorized credit card use is limited to $50, but most banks don't hold the card holder responsible for even that amount. Unlike billing-error disputes, which generally must be filed in writing, unauthorized transactions can be reported over the phone. And, there's no requirement to do so within 60 days.

In Emily Sachs Wong's case, reporting a charge as unauthorized may have made a difference in getting her money back.

Wong, a real estate agent in Chicago, says she filed a dispute when she couldn't get an explanation from her interior designer about credit card charges. The bank refunded her money.

But Gaynor, who worked with the same interior designer, disputed his charges as a billing error, rather than an unauthorized transaction. He didn't get his money back.

After losing the dispute, Gaynor agreed to accept $35,000 in furnishings he had originally rejected because they were delivered late. He did so, he says, even though the furnishings have "little value" now that he and his wife have replaced them. He's still out about $46,000.

Sarah Boardman, the interior designer, says the Gaynors had already received some furniture before they filed the dispute. They kept that. The rest of it, she says, had been shipped.

In Wong's case, Boardman says, the dispute cost her $12,000. Boardman believes the disputed charge was for two chandeliers. One, she says, had already been sent to Wong, and the other was waiting to be shipped.

The disputes have taken a toll on her finances, Boardman adds, because credit card companies pulled the disputed amounts out of her account while they were investigating. This left her unable to fulfill other orders and brought her close to financial ruin, she notes.

Disputes "should be resolved in 30 days, not this dragged-out process," Boardman says.

•Be prepared to arbitrate. Most disputes are settled between the merchant and the consumer. But your credit card issuer could also try to resolve it with the merchant's bank. If that doesn't work, the final step often is arbitration, where the issue is decided by Visa or MasterCard.

It's rare for cases to go to arbitration: At Visa, only one-tenth of 1% of disputes are decided in arbitration, spokeswoman Randa Ghnaim says.

Credit card disputes can last up to 270 days, including the arbitration process, although 99% of card disputes are settled much sooner, says Monteiro of MasterCard.

•File a complaint elsewhere. If you feel that your dispute hasn't been fairly decided, file a complaint with your state attorney general, the Better Business Bureau or a consumer advocacy group. Filing a lawsuit is also an option.

Josh Merriman, 59, got his money back days after complaining to his state attorney general about a $298 charge to his credit card.

Merriman of Shrewsbury, Mass., had signed up for a prepaid hotel deal. But when he checked with the hotel, he learned the stay would cost more than double what he was quoted.

When he couldn't resolve the issue with the merchant, he filed a dispute with American Express. He was denied a refund. That's when he called the attorney general's office. The regulator called the merchant, who promptly refunded Merriman's money.

American Express spokeswoman Marina Hoffmann declined to comment on the consumer's situation but says that the bank is "committed to resolving all inquiries in a prompt manner" for everyone.

Merriman is glad he sought help elsewhere. "It's amazing," he says, "what a call from the attorney general's office can do."