Practices
1. Wear or carry the scapular
2. To help another, place it in their vicinity (i.e. their room)
3. Pray, at least daily: "Immaculate Heart of Mary, pray for us now and at the hour of our death"
4. The prayer should be said for oneself and separately for each person to whom it has been given (unless they pray themselves)
5. No enrollment of any kind is necessary, but each scapular should be blessed by a priest (general blessing of sacramentals)
6. Have confidence in the effects of the scapular:
"The greatest graces come from using the scapular but these graces come
in direct proportion to the degree of confidence in me which the user has."
Promises/Benefits
1. Conversion of those who do not have the faith
2. Reconciliation to the Church for those who have lost/strayed from the faith
3. Assurance of a happy death
4. Strengthening of the faith for those already in the Church
5. Protection from Satan for those who wear or promote the scapular
http://www.allcatholicbooks.com/mary/scapulargreen.html