The Fraudwatchers Email Scam Checklist will help you to decide whether an email you have received is genuine or a scam. It uses statistical information about scam emails to estimate the probability that a particular email is a scam.
All you need to do is look through the suspect email for particular features. If you find them, tick the corresponding box in the checklist. If, after going through the checklist, you're still unsure, you can go to www.fraudwatchers.org and ask the experts there for their opinion.
The checklist lists a series of 'flags' that indicate that an email might be a scam. Not all scam emails involve all these elements. Some genuine mails might include one or two. But if you find more than a couple, you should be on your guard.
As you check them, the checklist background colour will change to reflect the level of risk: green is low risk, orange is moderate, and red is high risk. If the background is red, you should not consider responding to the email.