Man, for all the critics out there quick to point out that correlation is not equal to causation, nobody ever seems to explain what needs to be in place to actually show causation.
To establish causation you need 3 things:
1) Correlation
2) Temporal precedence. That is, you have to show that the cause occurs in time before the effect
3) A lack of other plausible explanations
If more people knew the above the world would be a better place. Even the Udacity statistics course failed to mention the above, even though they hammered home that correlation does not imply causation.