How can you tell if someone is a sociopath?
One of the hardest things about identifying sociopaths is how good a real sociopath is at hiding it. However there are some tells in behavior.
They tend to be charming and can morph into the type of person their target wants to see. They also tend to be pathological liars and see themselves as superior to others. They also delight in chaos and tend to create it whist quietly enjoying the resulting discord.
One thing that is hard is trying to identify a sociopath upon first meeting. These types of behaviors tend to be things that have to be observed over time.