Assign oxidation state 0 to any element in its free, uncombined form
Assign oxidation state equal to the ion charge for a monatomic ion
Use these standard values when applicable:
Group 1 metals: +1
Group 2 metals: +2
Fluorine: -1
Oxygen: usually -2
Hydrogen: usually +1
Sum of oxidation states in a neutral compound = 0
Sum of oxidation states in a polyatomic ion = ion charge
Let the unknown oxidation state be x
Set up an equation using the known oxidation states and the total charge
Solve for x
Check the result against common oxidation state rules