Originally published on Benscomputer.no-ip.org Aug 2009.
Whether it's a full network migration, or simply a change of Server Software, it is essential that any change is properly managed. Some changes occur after the IT department suggest them as the best course of action, whilst some are the result of managerial decisions. Whether it's to cut costs, to streamline the workflow or simply to acheive a more stable system, incorrect management of the change can be disastrous.
When preparing for the change, many people make the mistake of only planning for the change itself. You need to go further than that, plan the entire migration period. Create contigency plans, ensure that your disaster recovery plans are suitable for use with the new system.
This article assumes that as part of the change, you are installing a new managed network. If that's not what you are doing, the steps of planning are relevant, it's just that a number of the checks and possible deviations probably aren't.