JW’s believe that Jesus Christ’s death on the cross was to pay the penalty of Adam’s sin not the sins of all people.  Once Adam’s original sin was taken care of it makes the opportunity for all people to be rewarded with eternal life for their faith and good works.  Faith is necessary in the sense that persons cannot or will not change their lives to obey God without faith.  The basis on which God grants salvation is not simply believing or trusting God but “exercising faith” (John 3:16-18, NWT), that is, doing good works motivated by faith.

To redeem or ransom man from the grave means that God will provide a means of satisfaction of the judgment against Adam.”  (Life, 1929, p. 206)

Immortality is a reward for faithfulness.  It does not come automatically to a human at birth.  (Let God Be True, 1946 ed., p. 74)

Good works do not earn salvation, but they are prerequisites for it.  The required works fall into four categories (Watchtower, February 15, 1983, p. 12-13).

1. “Taking Knowledge” of God and Christ (John 17:3, NWT) by studying the Bible (through the guidance of the Watchtower).
2. Obeying God’s laws (meaning, all the rules laid down by the Watchtower).
3. Associating with God’s channel, the Watchtower organization.
4. Participating in the Jehovah’s Witness preaching work.