How do you work out the oxidation number of a atom in a compound?

To work out an oxidation state of an atom you need to assign the electrons on the atoms outer shell to the most electronegative atom.O>N>C>H. Electrons in the outer shell of two of the same atoms are shared equally. If a atom contains an electron own pair the electrons belong to the atom holding the loan pair. Oxygen normally has the oxidation state of negative 2, and Hydrogen normally exists with a plus 1.A neutral compound should have an oxidation state of 0.