Obtain a copy of your credit report and look for joint loans or lines of credit that you were previously unaware of.You won't have complete information if your spouse borrowed only in his or her name, as a secret card will not show up on your credit report, so ask your partner to pull his credit report as well, and read it together."You don't need to have joint accounts to get evidence," says Winston.

Among the red flags are unexplained and implausible charges for: Indeed, some expenditures will stand out dramatically (it's tough to justify Victoria's Secret purchases for a client), but others might not be such obvious markers. In the case of an unusually expensive gas bill, for example, ask about it and listen for nonsensical excuses.

"Cheaters come up with stories, like 'I had to go to Bob's and I knew you'd be mad.'" says Winston.

I had to smile.'" See related: How to cope when spouse's secret debts come to light, Divorce and debt: Advice on dividing up, paying off debt, Resist racking up debt to get back at cheating spouse We encourage an active and insightful conversation among our users.

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Not all are tripped up by the scent of an unfamiliar cologne or perfume, however.

Many are found out by their fishy charging and spending habits.

When you tell the person what you've found, "you'll be confronted with why you were snooping," she warns.

"So approach things carefully -- you don't know how dangerous of a situation you could be in." Remove your name from co-signed accounts and close them completely if you can as well.

"They eventually got divorced and he married the mistress.

Fifteen years later, the new wife came to me, saying, 'I know my husband is cheating' and brought the credit card statements that proved it.

"We use bank statements on a daily basis," says Marc Bourne, vice president for Know It All Intelligence Group in Bensalem, Pa.