  We establish that all strategy-proof social choice rules in strict preference
domains follow necessarily a two-step procedure. In the first step, agents are
asked to reveal some specific information about their preferences. Afterwards,
a subrule that is dictatorial or strategy-proof of range 2 must be applied, and
the selected subrule may differ depending on the answers of the first step. As
a consequence, the strategy-proof rules that have been identified in the
literature for some domains can be reinterpreted in terms of our procedure and,
more importantly, this procedure serves as a guide for determining the
structure of the strategy-proof rules in domains that have not been explored
yet.
