Make sure you have key players involved, particularly at management level. It would be unusual to have no resistors to the change, so you will need enough managers to ensure that any blockers can be cleared at this level.
Get the right skills from all the areas needed for the change to make sense to those involved. Match skills from the areas of the organisation that are likely to be impacted by or involved in the change.
Do the people on your coalition have strong, credible reputations already established across the organisation? These individuals must also be proven leaders in your organisation. This is different from position power above where their managerial experience is key, here we are talking about the ability to lead and have proven this ability within the organisation undergoing change.
At this stage the group is about guiding the change and will initially lead in the development of the vision (Step 3) rather than planning or managing the change. Conversations are about what, not how, change will impact the organisation. It is important that egos are left at the door, it is a team that is required to lead the change, not an individual.
Once selected the team with these characteristics need to establish trust and common goals that are "sensible to the head and appealing to the heart". With these things the organisation will be in a strong position to be guided through the change process.
Power / influence matrix
A power / influence matrix can be used to help map your coalition and identify any potential weak spots or characteristics missing from the assembled team. Use this information to correct the guiding coalition in the early stages of the change, you will be thankful for it later in the process.