Have the group get into a circle of no more than ten people. If you have more than ten people in your congregation then split into more groups.
Each person in the prayer circle says what their prayer request is, one at a time, going around the circle. After everyone has shared then have everyone turn to their left. The person who is now in front of them is the person that they should pray for first. Ask everyone to pray out loud at the exact same time and count them in.
After a suitable amount of time ask the prayer circle to change direction to the right and pray for the new person in front of them in the same way.