Both should be preceded by repentance. When we keep the covenants made in these ordinances, we are promised that we will always have His Spirit to be with us. The ministering of angels is one of the manifestations of that Spirit. We begin with the doctrine as taught by the Lord. During His ministry, Jesus taught that baptism is necessary for salvation.
Baptism is the first of the saving ordinances.
When we are baptized, we covenant that we will take upon us the name of Jesus Christ and serve Him and keep His commandments. At the conclusion of His ministry, Jesus introduced the sacrament of the Lord's Supper. When He introduced the sacrament, the Savior also gave teachings and promises about the Holy Ghost. On that sacred occasion known as the Last Supper, Jesus explained the mission of the Comforter, which is the Holy Ghost. The Comforter would testify of Him and reveal other truths.