UPDATE: August 2012 Power View Infrastructure Installation:  Step-by-Step and Scripts

General guidance for implementing SQL Server 2012 BI in a SharePoint 2010 farm (with one dedicated BI Server in the middle tier): http://msdn.microsoft.com/en-us/library/hh231687(v=sql.110).aspx
After the SharePoint 2010 farm is successfully deployed and tested  then:

1. Understand Kerberos and how to implement it for your environment: http://technet.microsoft.com/en-us/library/gg502594.aspx
2. For connection to data outside of the farm, review: http://msdn.microsoft.com/en-us/library/hh231678.aspx
3. Follow the detailed guidance to install the first SSRS Web [Service]  Application at: http://msdn.microsoft.com/en-us/library/gg492276(v=SQL.110).aspx on the dedicated app server that will be the “BI Server.”
4. Follow the detailed guidance for each WFE in the farm to add  the Reporting Services Add-in at: http://msdn.microsoft.com/en-us/library/hh479775.aspx. Additional information is at: http://msdn.microsoft.com/en-us/library/aa905871.aspx
5. After validating #1 and #2 are done validate via SSRS Verification  at: http://msdn.microsoft.com/en-us/library/ms143773.aspx
6. Follow the overall guidance to install the PowerPivot functionality at: http://msdn.microsoft.com/en-us/library/ee210654.aspx on the  dedicated app server that will be the “BI Server.”

a. Then the detailed installation guidance  at: http://msdn.microsoft.com/en-us/library/ee210708.aspx
b. Then the initial configuration guidance at: http://msdn.microsoft.com/en-us/library/ee210616.aspx
c. PowerPivot Verification is at: http://msdn.microsoft.com/en-us/library/hh231684.aspx