When I have taken over responsibility for a new area or activity the first thing I do is go around asking everyone what they do, how they do it, why they do it, and who they do it for. I also ask management and clients what they expect the area to be doing.
From this you develop a list of expected outcomes, the anticipated standards and the activities being done to meet those outcomes and standards.
You then chart the activities against the outcomes and the standards and determine if they are all still needed and if they are all still needed to that standard. Having established your activity base you then list the various resources being used to perfomr the activities. Then work with the staff to establish if they are the right resources to do those tasks and see if things can be done more efficiently or more effectively. Inevitably you will identify many activities that are no longer needed and can be safely dropped without harm.
When you have done all this you know what you are supposed to be doing, how it is done and what is used in doing it. Thus you can now make intelligent decisions about how you make the best use of your people and resources.
NB just about every worker knows a better way of doing their own job, so ask them, then examin how that affects others BEFORE you make any changes.
One place I worked at I had the people stop doing 132 tasks, 25% of the work, as we could not identify who they were being done for or why. In 6 years we only got complaints about 3 tasks. this made a lot of time and money available for what we were being paid to deliver.