Organic chemistry/Resonance drawings

One thing which organic teachers seem to love torturing you with, and which your therefore have to know, is drawing resonance images.

Resonance structures are often used in replacement of the Lewis structures which, in the mind of an organic chemist, has a flaw when it comes to showing where lone pair/pi electrons are stationed in the molecular structure. For electrons are not always to be found in one spot, as this typical Bohr model of a chlorine atom would have you believe, but are constantly zipping around at such a velocity that