A Born-Haber cycle shows how one mole of an ionic lattice is formed from its elements in their standard states and their standard conditions. You start with the elements in their standard states, and at each step you can only change one thing at a time, for example atomisation enthalpy or ionisation energy. If the enthalpy change is exothermic, the arrow from the first to second step points downwards and if the enthalpy change is endothermic, the arrow connecting the two steps points upwards.