Persistent communication is the key.  When a client hears that change is necessary, the first reaction is to find all the reasons it won't work.  This is especially interesting since the reason we are hired is to recommend change.  Providing a consistent message over time and allowing two-way communication helps to allay the fears of the client.  I have found that the same message to the same person can be received differently after some time has passed.  The first time the message is heard there is a lot of resistance.  Once the client has some time to come to terms with the change, they can truly hear what you have to say and begin to take steps to make the change happen. Not only is this true with the executives driving change, it is equally true to all those affected by the change.