A fallacy is the result of a faulty premise. The premise is faulty because of the reasoning for the argument is bad. Chapter 11 of the Epstein text discusses some different types of fallacies. I will discuss the "Bad Appeal to Common Belief" because I find that a lot of people fall victim to this type of fallacy because it is so greatly used in almost everything.
The Bad Appeal to Common Belief is based on the assertion that if everyone believes a claim to be true then it must be true. This type of fallacy is used all the time especially in advertisement or throughout an ordinary day. Those that are guilty of using this fallacy tend to use a vast population as support to their claim. For example: "everyone" or "most people" or "everybody who is anybody" are common indicators of this fallacy. Those that use this type of fallacy rely on the majority to determine the truth of their claim.
A recent example of Bad Appeal to Common Belief:
-Little Brother: Mom, can you get me a hotel room for after prom for me and my date and a couple of our friends
-Mom: NO!!! Absolutely not!
-Little Brother: Why not? Everyone else's parents are getting them rooms
My brother assumed that by letting my mom know that everyone else's parents were getting them rooms, that my mom would change her mind. Needless to say, it did not. LOL.
A better example would probably be...
It is okay to drink alcohol in moderation when you go out on the weekends because most people do, and they aren't all alcoholics.