Determine the atomic number, Z
Determine the number of shielding electrons, S
Use the formula Zeff = Z – S
For a specific electron, count only the electrons that lie between it and the nucleus
For valence electrons, include core electrons as shielding
For inner electrons, account for shielding from electrons in higher shells only if required by the method used
Apply Slater’s rules if a more accurate estimate is needed
Calculate the result as the effective nuclear charge, Zeff