Avoid friends questioning your IQ.
Don’t be lazy.
Factcheck emails before you forward them.
There are 3 good sites for this purpose, that I am aware of.
Non-partisan Politifact has a page regarding anonymous emails here:
http://www.politifact.com/truth-o-meter/personalities/chain-email/
http://www.snopes.com/
Snopes also tries to bust the occasional false rumor nut.
And www.factcheck.org brings to light political nonsense from both sides.