The 48 Laws of Power

Know who you are dealing with do not offend the wrong person. Study and spy on your opponent for however long it takes, this will pay off in the long run. Never trust the version that people give of themselves, it is utterly unreliable. Learn to tell the lions from the lambs or pay the price. The 48 Laws of Power, Law 19: Know their INS and outs before you even decide whether or not to deal with them.