1. Outlandish con tricks work BECAUSE they are outlandish

We all like to think we’re too clever to be taken, even though the number of suckers in this world far outweighs the number of con artists. One of the reasons for our misplaced pride is the sheer outrageousness of many con games – convincing someone that a stray mutt is really a prize breeder worth thousands of pounds, say. But the reason these cons work is precisely because they are so outlandish; they’re beyond most people’s normal frame of reference. This is why the Nigerian email scam works: you and I don’t normally deal with the exiled sons of Nigerian diplomats.

2. Beware any request for money up front

Speaking of the Nigerian email scam. Many cons – when you strip away the layers of embellishment that have been added are usually quite simple. They switch one package for another. They convince you that something is worth more than it is, whether it’s a beat-up fiddle they claim is really a Stradivarius or a mangy pooch fobbed off as a show dog, as mentioned earlier. One of the most common cons is the “advance payment scheme.” This involves asking for money now in return for a dazzling (and wholly fictitious) pay-off down the road, such as when someone phones to say you’ve won an all-expense paid cruise or a new vehicle, for free! You just have to pay the taxes on it, up front of course. Same thing with the emails asking you to transfer millions of pounds in Nigerian cash through your bank account. The basic principle is the same: money up front, nothing but hollow promises in return.

3. If it sounds too good to be true – it probably is

This is the First Almighty Rule in spotting any con. It is also a good guiding principle for businessmen and investors as well. Ask yourself “Why?” Why would someone give you a deal so outrageously tipped in your favour? Why would someone stop you on the street with a winning lottery ticket that needs cashing? (A common sting: The story is that they are illegal immigrants and can’t cash in their winning ticket without getting caught. The trick is that they’ve purchased one with yesterday’s winning numbers. Most people won’t check the dates stamped on the stub, but will be bedazzled by the size of the prize and will gladly buy the ticket. After all, what’s a few hundred pounds when the ticket itself is worth one hundred thousand! Or more!) But why would the lottery winner approach strangers on the street? Has he no friends, no acquaintances he could go through instead? No one? When an offer sounds too good to be true, there’s a reason.

5. Mind the Details

That’s where they’ll get you. One landscaper made a very good living pruning trees by quoting a low fee “per cutting” – only to charge the homeowners that amount per branch, not per tree. When challenged he would browbeat for wanting “something for nothing.” Likewise, if someone is peddling “100 per cent Authentic Spanish Fly aphrodisiacs,” check that the word “placebo” hasn’t been slipped in there somewhere. And if an online article promises you “Five Things You Need to Know About Con Games,” check to see that there really were five.

Spanish Fly by Will Ferguson is published by Harvill Secker, on January 17, 2008, £12.99

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