0. Install SSRS on the same machine where your one of the web front is.
1. Download the rsSharePoint.msi (Microsoft SQL Server 2008 Reporting Services Add-in for Microsoft SharePoint Technologies)
2. Run as admin msiexec -i rsSharePoint.msi SKIPCA=1. ( How to: Install or Uninstall the Reporting Services Add-in)
3. Locate under the temp folder( cmd: CD %TEMP% ) and run rsCustomAction.exe /i
This way you will see the actions that are being performed. Read it carefully in the real time - to catch the reason of errors in case rsCustomAction.exe fails
One of the issue I saw on that step is the Administrator doesn't have access to the Central Administration to activate Report Server feature.
The solution for this error is to add the administrator (the user that you use to run rsCustomAction.exe) as a site collection administrator.
To troubleshoot the SSRS errors - make use of it SSRS log file - %programfiles%\Microsoft SQL Server\<SQL Server Instance>\Reporting Services\LogFiles - SQL Reporting Services Log Files .