I recently attended a lecture by Carly Fiorina (in the magnificent Paramount Theater) on the topic of change. She made one point that I thought was particularly noteworthy (paraphrased):

By the time you've got consensus that change is necessary it's too late – you've lost your opportunity to competitors. The biggest challenge in leading change is building momentum early on, when it is most difficult to obtain buy in that change is necessary and agreement on what needs to be done.

If you are focused on getting everyone to agree, you are wasting your time. Get the important people to agree, keep the naysayers involved and engaged in dialogue, and in the meantime get started with smaller initiatives that will deliver early wins and build support  for the cause.

Fiorina is promoting the paperback version of her book. I haven't read it yet, so I can't vouch for it, but you can find it at Amazon:

Tough Choices: A Memoir
by Carly Fiorina
2006