You a tech junkie - you just upgraded to a new MacBook Air and are looking to ditch your old laptop online. It's only a couple years old, so you think you can easily get $450 for it. You pop onto eBay or Craigslist and hear from a buyer who says he's purchasing it as a gift for his sponsored child in Ethiopia. Nice gesture, indeed.

He says he's willing to pay you an extra $80 to ship it there. You agree, thinking it's an easy $80 and he must be a decent guy if he has an adopted child.

You keep an eye on your PayPal account for the money to be transferred in, until one day, when you finally get an email from PayPal. It tells you you're about to receive $650 for an item that you were supposed to ship - and as soon as you provide a tracking number, it will complete the transfer. The bad news is that email is a fake from the scammer and if you send the computer, in order to get the tracking number, the money will not be transferred.

How to avoid: PayPal will never send this kind of messages. Therefore, always wait for the money before you ship the item. That is, if you don't like giving things away.