What sort of suspicious behaviour should I look out for?

There are several types of scams that exist, many of which are email based. You should exercise extreme caution, especially with people who:

1. Are based overseas
2. Request payment via instant cash transfer methods
3. Request that you send goods before you receive payment
4. Claim to have a friend/agent who can pay you an amount greater than the value of your goods, then ask you to send them the difference