You can be not gullible, and they will find some way to get at you. Like to argue? They will jujutsu that. Think you are too intelligent to fall for this? They'll use that. If you find a trick that works, they learn and adapt.
Best way is to walk away. Easier said than done for a lot of people.
Robert Greene has a book about this. In one of the examples, he talked about a scammer trying to scam Henry Ford. Ford had no imagination. The scammer failed. Most people are not a Henry Ford.
I sold cars for a decade in the SV area. The amount of times I've seen engineers, lawyers, accountants, doctors and higher level executives make errors is pretty high. No one is 100% ON all the time.
The amount of times I watched very financially conscious people explain to me that they want to lease and then buy their vehicle afterwards, yet forget about sales tax during the buyout after lease end is comical. They were always surprised that even with a high money factor a lease to purchase still paid off...... Depending on how nice they were I would sometimes show them what the forgot.
I remember reading that there were entire product lines that omit you ever bought one mail order you were forever on the lists of “suckers who buy nose hair trimmers mail order” and they passed those lists around like candy.
Best way is to walk away. Easier said than done for a lot of people.
Robert Greene has a book about this. In one of the examples, he talked about a scammer trying to scam Henry Ford. Ford had no imagination. The scammer failed. Most people are not a Henry Ford.