Need Best practices for a SIEM environment/project

Hi

This is my 1st post here. I have been entrusted to re-vamp the ITIL (Incident,Change,Problem and Service Request Management) processes for 20 projects for a shared services projects model. I would like to know what would be the BEST PRACTICES for SIEM environment/project? Reason I ask this is, most of these 20 projects are supporting SIEM.

Appreciate any valuable inputs from this esteemed forum?

Thanks
Praveen