My brothers, if anyone among you wanders from the truth and someone brings him back,  let him know that whoever brings back a sinner from his wandering will save his soul from death and will cover a multitude of sins. (ESV)
There is a hymn which you may well know that has the phrase, "Prone to wander, Lord I feel it. Prone to leave the one I love." I believe that phrase captures the struggle that we go through as Christians. It does not take much for us to be wandering off the path of righteousness and caught up in another one of the enemy's deceptions.
There is a responsibility of those who are walking in the truth to "keep an eye" on their brothers and sisters. If we see someone wander from the truth we should make the effort to bring them back. This requires more than just checking to see if the wandering soul is living in accordance with the Church Bylaws. It requires us to love them, and so desire the best for them.
If we do our job as true believers we have the advantage of saving a person from death. What does James mean by that? We know that the wages of sin is death (Romans 6:23). Satan never tells the sinner that they are traveling on a road toward spiritual death. Nonetheless, that is the result when we pursue sin.
We should have a heart of compassion for those who wander. Before our salvation we all wandered from the truth. When James describes a "sinner from his wandering," he is describing all sinners. There is not a sinner who is not wandering from God's truth. As ambassadors of Jesus Christ we are to shine the light of truth in the sinners path and lead them to salvation.
How do you view those who are trapped in sin? With compassion? Put your compassion in action. Lovingly show someone the way to the truth of God in Jesus Christ.