There are actually 5 skills in applying Hess’ Law. According to science.uwaterloo and chem.libretexts.org these are the 5 skills.
- changing the enthalpy of the reaction whenever the equation changes
- interpreting the Hess’ Law
- applying the principle of conservation of energy to solve the problem
- sketching an energy diagram for any related reactions
- and lastly using the diagram to explain the Hess’ Law.