Consolidate .net web application

Hi,

I run IIS server for enterprise. There are 4 web servers and it serves 100++ applications. I plan to re-design by grouping the application into small group and create IIS web server on virtual machine e.g. 2 set of server and each set has 2 server. 

I would like to ask for experience IIS admin. Is there any publish document for the guideline/best practice for the internal shared web server?

Or, do you have any suggestion on how to group the server?

Thank you in advance.

Chaba