Things to Consider:  Be careful who you give out personal information to. Most legitimate sellers who accept credit cards, do so through secure third party. Therefore they do not need your credit information directly (IE: via email, phone, fax, etc.)

Course of Action:  In a case of fraud, when you've made the purchase on your credit card, you must contact the credit card issuer as soon a possible and report the fraudulent activity. Then request that they initiate a chargeback to retrieve your funds.

Things to Consider:  There are many fake escrow services out there that may try to steal your money. Be sure to use a trusted or well known escrow service such as escrow.com
Also remember escrow services are generally only used in high priced transactions.

Course of Action:  In a case of fraud (ex: item is not received or is damaged), contact the escrow service immediately and explain the problem. Make sure you tell them not to release funds until situation is resolved. You can request that they return your payment if your seller refuses to cooperate or if the item never arrives.

Things to Consider:  PayPal only offers fraud protection when buyers send payment to "verified" paypal sellers. If you make payment to a non-verified seller, chances of recovering funds are minimal.

Course of Action:  Contact PayPal as soon as possible, Explain to them in detail what has happened and wait to see if they can recover your funds. If credit card was used through paypal, consider initiating a chargeback as discussed in the Credit Card COA.

Things to Consider:  If the person you are sending money to steals your money, there is little you can do about it. Always check feedback, talk to former buyers, check the Better Business Bureau, or try to call the seller before sending payment.
You should avoid this form of payment if possible!

Course of Action:  Little you can do after payment is sent. Contact the post office and file a fraud report; do the same with law enforcement in both your location and theirs. You probably won't get your money back, but may prevent others from losing money to the same person.

Things to Consider:  Services like Western Union are set up for sending payments to people you know, NOT complete strangers. Since these services are often used when people lose wallets or credit cards, no ID is required to gain access to funds, and funds can be picked up at any location worldwide. This form of payment is used for most online scams.

Course of Action:  There is absolutely no course of action. If your funds are stolen, there is no way to track down the scammer as they need no address, identifcation, or personal information, to steal your funds. After payment is sent your money is as good as gone.