Use of a two-dimensional grid to locate a transition state

For bond making or bond breaking reactions involving exactly one bond being made and one bond being broken

 The  GRID calculation can be used.  In this, two coordinates that are important in the reaction are chosen, and the Potential Energy Surface for the optimized geometry is generated for all reasonable values of these coordinates.  Visual inspection of the resulting map can usually provide a guide to the transition state.  Once the approximate transition state is determined, it can be further refined using TS.