The latest issue of the environmentalist includes an article I've written, entitled "who can help me make this change?". In it, I share an approach I've used successfully in training courses and (as my daughter would say) in true life: it helps people to systematically identify key internal and external players who can help them bring about the change they want to see. If a particular person or group are crucial to making the change happen, then you want them to be supportive of it. Ask them what they'd like to see happening, and how you can help them. Find common ground and enlist their support.
If someone is already very supportive, but not really needed, then see what they can do to influence or recruit those who are needed. Or enlist them to support you.
Remember, the art of engaging people to help create transformational change involves listening and letting go.