Server Rack Configuration Best Practices

I am looking to gather information on best practices for the installations of servers into a rack environment. We are mainly using IBM Xseries servers with the odd old Compaq proliant thrown into the mix. I am looking to get info on what is required in the racks and where is the besk posstion to place the servers. Also i would like to know if there are any industry standards for Rack configurations etc, to maximise server uptime whilst keeping cost and heat down to a minimum.

Any further questions please ask.

Many Thanks
David