The Diocesan Bishop appoints the Dean (Vicar Forane), having consulted the priests who exercise ministry within the deanery. The Diocesan Bishop may, however, enact particular law for a diocese, to determine another mode for choosing the Dean (e.g. election, or some formal method of consultation prior to appointment).
The Bishop may appoint any priest as Dean and the office is not necessarily attached to any particular parish. The appointment is to be for a precise term and does not enjoy stability. For a just cause the Diocesan Bishop may freely remove the dean from office
Over and above any special faculties that he may enjoy from Diocesan particular law or by delegation from the Diocesan Bishop, the Dean should be the key element in the pastoral life of the Deanery. His role is first of all that of promoting and coordinating, supporting and helping the local priests and deacons within his deanery. After that he may be considered a trouble-shooter to solve local problems. As with all ecclesiastical offices, the letter of appointment should specify the rights, duties and obligations attached to it.
The Bishop describes the role of Dean in the document found here.