Managers who share information freely about change are much more easily able to smoothly effectuate change. It is when people don't know what is going to happen that paranoia sets in, and people are not motivated to cooperate. I remember working for an agency some years ago at the point at which personal computers were introduced. There was no discussion of the change, and many of the secretarial staff were fearful for their jobs. Production fell significantly during this period, and this was so unnecessary.
Let's say that something has changed in the firm and some employees will have to do different jobs than what they're used to. The manager can and should explain why this is happening. Then he/she should be sure the workers who have to switch jobs get enough training to feel comfortable.