Prove Everything… But How Exactly?

The Bible tells us that we are to prove everything and hold fast what is good. What does this mean? Do we have to convince ourselves of the Truth and make it part of our being? What consequences does this have for our conduct towards others? Does one have to be appointed by God to be a teacher of the Truth? Are God’s ministers necessary so that one can even come to and understand the Truth? How do you know whether someone is a true or a false minister? Are we admonished not to argue with others about the Truth? Why can discussions about God’s Word be very dangerous?