Add up available valence electrons:
C = 4, H = (3)(1), Cl = 7 Total = 14
Join peripheral atoms
to the central atom with electron pairs.
Complete octets on
atoms other than hydrogen with remaining electrons
Make carbon the central atom (it wants the most bonds, 4)
Occurs when more than one valid Lewis structure can be written for a particular molecule.
These are resonance structures.
The actual structure is an average of
the resonance structures.