Whether you are upgrading one version of CRM or three, it is very important that you run through the upgrade prior to the night you upgrade your production environment. Once you have your dev environment upgraded and you build your solution of upgraded customizations, go through a test upgrade in a copy of your production environment. This serves several purposes:

• When importing solutions into upgraded environments that contain the components in the solution, it is very common to get some kind of error. By testing the upgrade you get an opportunity to resolve potential solution conflicts in a lower pressure time than the production upgrade night when you are limited in time.
• Going through a test of the complete upgrade will give you exact times for each of the steps, so you will know how much time you will have to allocate to your maintenance window.
• While doing your end-to-end upgrade test, document the order in which the items are performed. For example, some tasks like importing your access team templates need to happen prior to importing your upgraded customization, while some tasks need to happen post customization import. For example, say you are upgrading a CRM 4.0 environment that has the Business Productivity Workflow Accelerator installed. You will need to import your updated workflow customizations first to remove the dependencies on this solution, then remove the accelerator plugin assemblies.
• The document you create can become your “playlist” for upgrade night, and you will avoid having to pull an all-nighter or deal with unexpected surprises during the upgrade.