Hi Kishore
Preparation from PI side ---should include the evaluation of interfaces-to see if all functionality will be supported in upgraded version versus the version you are moving from (Dual Stack- then check if ccBPM/WSRM is used in interfaces/set up ICO from classic configuration). Plan on how you would like to cutover the interfaces (in Batches or all at once- depending on the number of interfaces and business requirement/agreement).
If you are going to do the basis task as well, from PI side run the post installation set up wizard (e.g PI EHP upgrade).