I have a few rule-of-thumb notes from having worked in and alongside change programmes. These are important whether or not you use consultants:
* It's important to start at the top - unless the CEO and directors are keen, and prepared to shift their own behaviours, chances are it won't stick, or will just be paid lip-service to.
* Don't rubbish everything that's happening now - chances are there's some good stuff going on.
* Find what's working now, what matches what you want (individuals or groups) and use them as good examples.
* Don't leave it all to the consultants: for it to stick, people within the organisation need to have been fully involved. It mustn't be something that's "done to" people.
* Don't just rely on workshops. Find a way of integrating what's happening into everything and look at what the blockages are. A good question to ask, before you start, is "What's stopping us from being proactive, commercially aware and involved?". Ask (personally, not with a questionnaire) teams, individuals, and senior managers. You may find some systemic things that need changing first.
* Read the question that prompted this answer here.