The cheapest way in is a person
Breaking modern encryption is hard. Convincing a tired person to type their OTP into a form is easy. That is why the large majority of successful attacks start with a message, not with code.
You are not learning this to run these tricks. You are learning the shape of them so that you notice one while it is happening to you or to your family.
The four levers
Nearly every social engineering message pulls at least one of these.
Authority. The message claims to be from someone you obey — the bank, the placement cell, the police, the head of department.