The following is taken from my self-improvement book The Unused Path. It's a simple way to evaluate proposals, arguments, and behaviors to see if they pass the 'makes sense' test. It can help you avoid being deceived, and it begins with a simple piece of advice:
Watch for inconsistencies.
When something is inconsistent, it doesn't match or fit what's around it. Train yourself to notice inconsistency wherever you find it, but especially when dealing with other people. Do their deeds match their words? Do the words they're speaking to one audience match what they say to a different audience? Does their behavior under one set of circumstances match their behavior under others?
If the answer to any of those questions is no, it's possible they may try to mislead you.
Here's an example: Some people will attempt to convince you to stop using an item that works, just because it's been around for a while.
There's an apt saying on this topic. "Don't throw out the old bucket until you're sure the new bucket doesn't leak."
Let's say someone is trying to convince you to replace your 'old' bucket with a new one they happen to be selling. The world is full of people peddling leaky buckets, and they can offer arguments that seem convincing. They'll tell you it's made from a better material. They'll tell you it's lighter and stronger. If there's money in it, they're likely to tell you anything.
How might you figure out if they're playing you, without actually getting played?
Look for inconsistencies. Examine their argument to see if it logically supports the action they recommend. Question it from different angles to see if it makes sense all the way through.
Let's continue with the bucket example. They're telling you the new bucket is stronger and lighter. Is this important, even assuming it's true? The old one is working well for you, so it's obviously strong enough to do the job. Does it matter that the new bucket, when empty, is lighter than the old one? When either bucket is full of water, the weight of the water is what makes it heavy—and that's the same in both buckets.
Those are two inconsistencies right there. It may be a good idea to stop considering this purchase—and get away from that person.
You can apply this technique to arguments, promises, and even excuses you may be offered. Consider each part of what you're being told separately, and then look at the whole thing together. Does anything they're proposing seem illogical, impractical, or unlikely? Dig into that inconsistency, and you may avoid getting fooled.
My book The Unused Path contains numerous straightforward tips like these for navigating life with a clear head. It also contains step-by-step advice on solving problems, budgeting your money, managing your time, getting sound advice, and more. It's available in ebook or print from Amazon and Barnes & Noble, and I hope you'll check it out.