It seems that the whole Battlestar Galactica TV series is based on the simple fact that the humans are totally unable to tell the difference between a Cylon and themselves! Although it seems that there was an attempt to train the military in this, but somehow the message must have been lost somewhere along the line. Check out video number twelve below on how to spot a Cylon.
According to UGO this is how these videos would have made spotting a Cylon easier;
Of the many dangers colonial officers will face, the Cylon menace is one of the most deadly. But do not worry, we have put together a helpful and informative training video. So next time a Cylon is in your midst, you will easily be able to identify them. Long live the Twelve Colonies!
Source: Geeks Are Sexy