Baselining is one of the most important phase before we start with proper MPs tuning.
To make baselining easier I have discovered free tool which can be most beneficial for this part of engagement.
Performance Analysis of Logs (PAL) Tool
Tool contains predefined interfaces for all MSFT technologies and can be great assessment tool to get clear picture about MSFT technology performances in customer environment.
I would recommend collection of data for few days (between 1-7) as baseline sample.
(great thanks to PFE - Krunoslav Mihalic, who intoroduced me with this tool)