It is a common misconception that dangerous people are the grungy, tattooed apparently anti-social types we often come into contact with.  In fact, the people who are potentially the most dangerous to us personally are the ones we think we know.

I have been threatened with great harm and put in great danger by those individuals who did the most to appear personable and trustworthy, flattering and generous.  That is who you have to distrust the most.

As I have written several time before, beware of Greeks bearing gifts.

There's a lot of good information out there on sources and methods.  Experts have published  tons of very useful stuff that you can use to protect yourself from useful idiots and pros, as well.  

Knowledge is power.

Know your enemy.

If there is any doubt, there is no doubt.