Azaan/ Adhan (Call for Prayers) is recited before Iqaama (Set up for Prayers), they are usually made when time for Salah/ Namaz/ Prayers have set in. Muslim sects differs slightly in their formats, even with compulsion/ weight-age each sentence carry, same happens with different Shia centers, following is conventional Shia Azaan.
Prophet Mohammed ordered Azaan after his migration to Madina, the person who delivers azaan is called 'Muezzin', first Muezzin of Islam was Bilal s/o Ribah who was a faithful companion/ Sahaabi of Prophet Mohammed. After the event of Ghadeer (Announcement of Ali's vice-regency), Salman Persian another faithful companion/ Sahaabi of Prophet Mohammed delivered azaan, this time he is reported to have recited: Ash'hadu anna Aliyyun Wali'allah (I testify Ali is Vicegerent of God). People instantly took objection and Prophet Mohammed himself made them know that this was exactly what he had announced just then.
Shia do not add sentences like, 'Prayer is better than sleep/ Assalaatu khaerum min an naum' in dawn azaan/ prayer's call because they were added by Umar s/o Khattab the second caliph during his reign but he did not had any authority to do so. Umar s/o Khattab is also noted in Shia history to have removed 'Hayya alaa khaeril a'mal/ Hasten towards best activity' for abrupt reasons. Shia also do not have any extra azaan on friday which again was an innovation, this time by Uthman s/o Affan third caliph during his reign.