http://www.bnet.com/blog/entry-level/how-to-hone-your-bs-detecting-skills/3536?promo=713&tag=nl.e713

• Determine what serves the speaker’s self-interest. Whenever someone is presenting a point of view, you owe it to yourself to consider how their opinion might correlate to their own self-interest. After all, there must be some reason they have to make the argument to you in the first place. And that reason more likely correlates with their own self-interest than with yours.
• Question the data. We live in a world of pseudo science, skewed sample sets and anonymous experts. Don’t accept anything as an important truth without first examining the source.
• Watch for truth qualifying statements. “To tell you the truth” or “Let’s be frank” or “I have to be honest…” are all statements that beg the question – “Are we starting to be honest just now?”
• Listen for name dropping. Credibility should always be derived from the strength of the argument, known facts and/or the reputation of the person present. If absent prominent people are the backbone of an argument, you should be suspect.
• Notice confusion in response to logical counterpoints. This type of response is meant to undermine your confidence in the soundness of your counter argument without seeking to specifically or factually oppose the point itself. Watch out for confusion when there should be none.
• Beware of the obvious. If a conversation provides you with one obvious thought after another, wait for the end of the train of thoughts as it is typically an illogical conclusion. After getting into a “yes…yes… yes…” rhythm, you may easily accept a well placed random conclusion or mistruth.