The oxidation number of an atom in its elemental form is 0
The oxidation number of a monatomic ion equals its charge
The sum of oxidation numbers in a neutral compound is 0
The sum of oxidation numbers in a polyatomic ion equals the ion’s charge
Group 1 metals are usually +1
Group 2 metals are usually +2
Fluorine is always -1
Oxygen is usually -2
Hydrogen is usually +1
In metal hydrides, hydrogen is -1
In peroxides, oxygen is -1
In superoxides, oxygen is -1/2
Halogens are usually -1, except when combined with oxygen or a more electronegative halogen
Assign known oxidation numbers first
Use the total charge to solve for unknown oxidation numbers
Check that the final oxidation numbers add up correctly