Make sure your purchases and information are secure -- Use credit cards to limit your financial exposure, look to see if the web transaction is securely encrypted, and be careful with your passwords. More information.
Learn to spot unscrupulous marketers and fraudsters before you shop -- Learn to spot a scam before you fall for it. Also, find out where to look to see if marketers will misuse your personal information. More information.
Check company policies and keep records of your purchases -- Before you buy, make sure you're aware of the company's policies on returns, warrantees, etc. After you buy, keep good records of your purchases and keep an eye on your credit card statements. More information.