As a neuro-axiologist, I study and apply value SCIENCE integrated with neuroscience to the process of organizational change and transformation. We deal with personal and organizational values on a daily basis.
With the limited space I have, let me suggest:
1. Understand that Values are properties, attributes, or characteristics that drive decisions and behaviors Most often, they are NOT actual characteristics of every person in a group: they are an ideal that you want to develop into a characteristic.
2. For them to have power and meaning, these values must be linked to purpose - your mission and/or vision.
3. Therefore, first make sure you are crystal clear about your mission and vision, including WHY you have them and the value that their achievement can create. This step needs to be done first and ought to be done by the leadership team only.
4. THEN bring the rest of the group together to indentify the Values that support the Vision and Mission and that everyone in the group can get behind. The values you come up with will reflect properties, attributes,a dn behaviors without which you cannot fulfill your mission and vision.
5. Finally, turn your Vision, Mission, and Values Statements into questions that people will use to make decisions and to hold each other accountable. For example, "Does this _____ (choice, policy, action, etc.) support our mission of ____? This brings meaning, power, purpose, and sustainability. Teach these "Mission Critical Questions" to every employee from day one. Use them to hold people accountable and develop people by asking the questions whenever they are faced with decison or have made a poor decision.
When the above process is followed, the results are exponentially better than any other process we've seen.
Lastly, I would highly recommend that you hire an outside facilitator. An good facilitator won't have their own agenda and can help keep the conversation on track and moving forward.
Hope this helps.