I have found Action Research approach of Chris Argyris the best for OD intervention. This place is too short to give you the entire method. But I am posting some questions that you could ask the group you are intervening in
The basic action of reflection is to ask questions such as:
• What do we think is going on here?
• What did we intend to happen? What did happen?
• How is what I am observing connected with deeper theories about how things work?
• Here is my view and how I arrived at it; how do others see it?
• What assumptions are we making?
• What pressures seem to be at play in the system?
• What role am I playing?
• What am I thinking? feeling?
• What leads me to think and feel the way I do?
• What am I going to do with my insight?
I have asked people to reflect on these questions as they go about their routine task meeting. The person who has an answer to some or any of the questions is expected to stop the meeting and offer a hypothesis on the process that is unfolding in the group, the group reflects on it and then continues its task discussions