Whether using CSM or SAMPJCL, install the base product and then apply all PTFs. Do not do both in the same run.
Read Release Notes for all skipped releases. Understand new features or open a helpdesk issue if further clarification is needed.
The z/OS Installation guide is helpful and contains detailed info on CEINSTAL and ITINSTAL.
Review the Technical Requirements to make sure the 3rd party products are supported. If after reading and there are questions, open a helpdesk issue for confirmation.
Get a DB2 DBA or Admin involved to run the installation jobs (CEJOBnn and ITJOBnn).
The same changes made in the prior release for user exits, CLISTs, skeleton, or sample libs member must be made to the library members in the new release.
If using the z/OS IT and changes were made to TIXMVSRI and/or TIXMVSLM, migrate the same changes to the new release. Do not use the old release members to build new scripts.
If using CA Gen Direct Connect for CICS, we recommend using the Multi-Socket Server Listener. This will support the new features going forward.
If upgrading from Gen r7.6 or 8.0 to Gen 8.5 or 8.6, the applications do not need to be regenerated or reinstalled in most cases. A case where reinstallation for some modules is required if maintenance was not up-to-date in Gen r7.6 or 8.0 prior to moving to Gen 8.5 or 8.6.
If running batch jobs, do not use the prior release JCL. Build the JCL with Gen and then make modifications as needed.
Test thoroughly as desired for your site especially the most used transactions.
When in doubt about any setting or usage, open a helpdesk issue for confirmation.