It is always good to do the preparation before performing an upgrade of the production environment. The checklist in this article is for helping you to reduce the risk which will bring into production by the upgrade.
Draw up a rollback plan for upgrade failure based on the same documentation.
Test the upgrade procedure in a Test environment
Validate UI, Tasks, API works in a Test environment
List out the machines that need to be upgraded in a Production environment
Back up the Qliktech folder, Root folder and all of the folders you place documents in Production Environment
Check parameters if you changed from default values in config file after upgrade. Sometime parameter is back to default value after upgrade. i.e. <add key="EnableBatchMode" value="false"/> in distributionService.exe.config