Apparently, the two most common types are the "overpayment" checks, supposedly for goods sold in the classifieds, and lottery or sweepstakes winnings, which are often represented as a prize from a foreign lottery. Which is why we here at the BW True Crime Desk rely solely upon Ed McMahon for our fake checks. It's how we afford the life we lead here, lighting fake cigars with fake dollar bills.
Wasden's advice includes a well-worded scolding to anyone who hasn't yet realized what century we're in: Use the Internet, already. You losers ever heard of PayPal? Also, when in doubt, and you weren't expecting checks full of fake cash in the mail (unlike, ahem, us) you ought to just take the thing to your bank. And before depositing it and taking out a loan on a new boat, ask them if it's real. And prepare for disappointment.