How can I install OS X Lion on a new HDD?
If you have a copy of Lion already downloaded you can use the instructions here to create your own. The installation image is in the downloaded package and can be restore using Disk Utility.


  
  Add the InstallESD.dmg image to Disk Utility
  Select empty USB drive and go to restore tab
  Make the InstallESD the source
  Make the USB Drive the target
  Click Restore
  


Alternatively you can purchase a Lion install USB drive from your local Apple Store or online here for $ 70.00.

If you only redoing the actual OSX partition and already had Lion installed, you can use Cmd+R during boot to access the Recovery partition which will allow you to download OSX Lion or restore from Time Machine.

Mountain Lion is only available to registered developers with access to the Mac Developer Section, but the manual process above works exactly the same.