There are lots of situations when you realise that it's time to change things. If you want to know where to start you have to look and see where the first signs of readiness are. If you do that, you'll find it much easier to explode the mould and reduce it to dust OR open it cleanly on the break line. Breaking moulds always seems wasteful, and, if it involves peoples lives then that kind of change can be too violent.
To switch analogies, Kurt Lewin likened the process of change to the process of freezing water:
You start as ice, thaw to water and reshape and then re-freeze to hold the new shape.
I love this picture of change and how to go about it. To take it one step further, think of all the conversations you've ever had where people are just not quite satisfied with the status quo; those are the first droplets of water forming on the surface of the ice.
Remember, the first people to see that a change may be necessary are NOT usually the ones in the middle of it.
I can think of times when situations were 'un-freezing' all around me; absolute chaos!
Then there are dreams and 'Holy Discontent', great forces for change.
If you find those cracks, or droplets and harness their power, you will find that change starts to shape itself. You'll soon find that early adopters will be able to buy-in to what your doing and you should also see that shared sense of ownership, that makes change stick.