Righteousness from God comes through faith in Jesus Christ to all who believe. There is no difference, for all have sinned and fall short of the glory of God, and are justified freely by His grace through the redemption that came by Christ Jesus. (Romans 3:23-24)
In Acts 16, the jailer asked Paul and Silas a fundamental question: "Sirs, what must I do to be saved?" Paul and Silas responded, "Believe in the Lord Jesus, and you will be saved -- you and your household." We are justified solely on the basis of the finished work of Jesus Christ on the cross.
Justification can be defined as the act by which an unjust sinner is made right in the sight of a just and holy God. Justification occurs at conversion, when Christ's righteousness is imputed to the believer as result of the believer's exercise of faith in Christ. Faith itself is a gift of God: "For it is by grace you have been saved, through faith -- and this not from yourselves, it is the gift of God -- not by works, so that no one can boast" (Ephesians 2:8-9).
Works plays absolutely no role in justification. This is one element that distinguishes the Christian faith from all other worldviews. Yet we often hear the cults quote James 2:24 as a "proof" that justification is by works, or is the result of a combination of faith and works, since James says that "You see that a person is justified by what he does and not by faith alone." That interpretation violates the context of James 2, and clearly contradicts other Scripture verses. What James is saying is that, while we are justified in the sight of God by faith, we are justified in the sight of men as result of our works. Works is the outward evidence of having received justification -- it is not the method by which we are justified. Justification is by grace through faith alone.
Therefore, since we have been justified through faith, we have peace with God through our Lord Jesus Christ, through whom we have gained access by faith into this grace in which we now stand. (Romans 5:1-2)