My group did this last week, and while some were hesitant at first, all of us enjoyed the exercise and came away having grown a little bit.
Here is a link to the pdf of this study.
The rules are really quite simple:
Begin with one person adding one item to one list.
Moving clockwise, everyone takes a turn adding one item to one list.
Each person must choose a different list each time it is their turn.
Each person may only "pass" once.
Once your group has filled all the lists ask two questions to the entire group:
1) What is one item someone added to a list that made you smile? Why?
2) What is one item someone added to a list that challenged you? Why?
Encourage everyone to keep their lists handy throughout the week as a reminder of how to pray for each other, passages they can be encouraged by, or anything else which might benefit them!