Grieving is a natural part of loss but not an easy one. The loss can be anything from a job loss to the loss of a loved one. (Please, see my article on God, Do You Love Me?) But those who are in Christ have hope - Heaven. Heaven is a place where God is and He promises to wiped away all our tears. How glorious that will be.
There are a couple of books on loss and grieving in my reference section. It is hard to know what to say or how to act when someone is tramatized by loss and in the process of grieving. My advice, as one who has experience the loss of a spouse, is not to give advice unless asked. Be a good listener and offer a hug in quietness. Yet, the best thing that can be done for someone in any loss situation is being proactive with the teachings of Christ. The greatest gift you can give any person is the knowledge that the Lord is on thier side regardless of life's experiences. Don't wait to teach them, and all people you come in contact with, the true Gospel of Christ and then "brothers . . . you may not grieve as others do who have no hope (I Thessalonians 4:13).
I encourage you to teach others, daily, about the hope in Christ.
The Lord's humbled . . . John A. Reeves