Answer is: to draw the best Lewis structure, you should minimize formal charge.
When determining the best Lewis structure for a molecule, the structure is chosen such that the formal charge (FC) on each of the atoms is as close to zero as possible.
Formal charge (FC) estimates the distribution of electric charge in a molecule.
The formal charge of any atom in a molecule can be calculated with the equation: FC=V-N-B/2.
V is the number of valence electrons of the neutral atom in ground state.
N is the number of non-bonding valence electrons on atom in the molecule.
B is the total number of electrons shared in bonds with other atoms in the molecule.