This is a good article on 10 ways to spot email scams:
http://www.switched.com/2009/10/26/10-ways-to-spot-an-e-mail-scam/
Anyone asking for personal information, credit card information or saying you won money via email is probably a scammer. Remember not to click links in emails unless you are sure they are legitimate. Also remember scammers can pretend to be a trusted source. Check the article for the top 10 ways to spot email scams. If in doubt, delete the email without opening it.