How to calc. the value of screening constant while finding the effective nuclear charge?

Screening constant is calculated using Slater’s Rule as follows

1. The electronic configuration of given element is written as follows(1s)(2s,2p)(3s,3p)(3d)(4s,4p)(4d)(4f)(5s,5p)(5d)…
2. Electrons to the right of the electron of interest do not contribute to shielding constant.
3. All other electrons in the ns and np group contribute to an extent of 0.35 each to the screening constant except 1s group which contribute to an extent of 0.30.
4. All the electrons in (n-1) the shell contribute to 0.85.
5. All the electrons in (n-2) or lower hell contribute 1 each.
6. For d and f electrons rule 1 to 3 are same. In place of 4 and rule 7 is applicable
7. All the electrons in the group lying to left to the nd and nf group contribute 1.0 each