Write the chemical formula
Assign oxidation numbers to elements with fixed values first
Group 1 metals = +1
Group 2 metals = +2
Fluorine = -1
Oxygen = -2
Hydrogen = +1
Sum of oxidation numbers in a neutral compound = 0
Sum of oxidation numbers in a polyatomic ion = ion charge
Let the unknown oxidation number be x
Set up an equation using the total sum rule
Solve for x
Check that the oxidation numbers add correctly
Remember common exceptions
Peroxides: oxygen = -1
Hydrides: hydrogen = -1
Oxygen with fluorine can be positive
Halogens are usually -1 unless combined with oxygen or a more electronegative halogen
Use the oxidation number rules consistently