The Bible is our final authority (2 Peter 1:3). We have no supplemental creeds, manuals or councils to interpret or dictate the meaning of Scripture, so churches of Christ are "autonomous": each one is self-governed (with no earthly headquarters), for Jesus is the head of the church (Colossians 1:17).
Like the human body, each member of Christ's church functions in different yet equally important areas of service (1 Corinthians 12:12-31).
The Old Testament (covenant) is valuable for our learning and example (Romans 15:4; 1 Corinthians 10:6-11), but the old covenant was fulfilled at the cross and was superceded by the New Testament of Jesus Christ (Hebrews 8:6-13 ; Galatians 3:23-29). None can keep the old law and new law at the same time (Romans 7:1-6), so today we must look to the New Testament as our guide to eternal salvation.
Regarding salvation, one is saved by God's grace through obedient faith. GRACE could be likened to God's hand reaching down in love and mercy to mankind, while FAITH could be likened to man reaching up in obedience to accept God's grace.
The WAY of salvation is a PATTERN that can be identified and obeyed (Romans 6:17-18): FAITH comes by hearing God's word (Romans 10:17) and is essential to one's salvation (Hebrews 11:6). Faith (or belief) must be in God and in Jesus Christ as the Son of God (John 8:24). A person must realize that disobeience to God is sin (1 John 3:4) and REPENT (Luke 13:3). A penitent heart leads one to publicly CONFESS his faith in Jesus (Romans 10:10) and to be BAPTIZED for the forgiveness of sins (Acts 2:38).
Baptism is just as essential to salvation as faith or repentance or confession (1 Peter 3:21). At baptism, the old man of sin is buried and the new Christian is raised to walk in newness of life (Romans 6:1-4).
Obedient faith will be demonstrated by good works (James 2:24), so Christians must be active in sharing the good news about Jesus (Matthew 28:18-20) while striving to be good examples in all things and helping others along the road of life (Titus 3:1-2; James 1:27).