Many enterprises are not able to adapt to changing business requirements. One of the solutions to this agility problem is the usage of service-oriented BP modeling. Meanwhile, their existing BP modeling does not consider the potential services in Legacy IS (LIS) or from partners, in order to have a service-oriented BP modeling that promotes agility. This requires a complete reengineering of the LIS and the BPs into services realized by business objects. In this modeling paradigm, BPs are represented by specialized services, having separated concerns such as controller service, state service, and worker services. This paper provides guidance, by using techniques to retrieve business knowledge embedded in LIS and transform it into services towards moving from as-is to to-be BPs. These techniques are: (i) reverse engineering LIS, by extracting services from traces of BPs, and (ii) reverse engineering from the enterprise service portfolio or reusing partner and provider services.