Flexibility is a key characteristic of several business process management domains among which software processes. In such settings, dynamic decisions can deeply affect process executions depending on the current circumstances. Therefore, the paths to fulfil the process goals are not fully predetermined. However, high flexibility does not mean chaos: a set of key process rules still delimits the execution space. One of the most renowned paradigms for managing flexibility by design is the declarative approach, which aims at defining processes through their core behavioral rules, thus leaving room for adaptation when necessary. To achieve its full potential, the declarative approach requires a paradigm shift in process thinking and, therefore, the support of novel tools. The goal of this tutorial is to distill the declarative approach down to its core concepts. In the first half, the tutorial focuses on the main principles of declarative Process Mining with the Declare declarative language. The second part provides practical examples and exercises using the RuM toolkit and the Declare4Py Python library.