Before most of you add comments I would highly recommend you go to your local university, enroll, sign up for some basic logic classes (Sentential Aristotelian preferably) and study hard for about a year. Unfortunately most will never go through this kind of rigorous critical thinking training. I understand why, college is expensive, books are heavy, and your parents and most of the world encourages highly illogical ideas on a daily basis. Thinking clearly makes most peoples head hurt :( As a substitute I will offer a crash course in Logic here via some great links to better sites. Some of these items will seem very obvious (to the smart ones) but I felt that I should still put them out there (for the dumb ones).
Basic Logic: What is Logic?
Sentential Logic
Fallacies & Biases
A List of Common Fallacies