At WinHEC' 06 Microsoft released an important whitepaper that provided insites and best practies for Code Signing.  This paper includes Code-Signing Bacics, Signing Technologies in Windows, Digital Signatures in Windows, and a comprehensive view of Code-Signing Best Practices. 
To access this whitepaper please access this URL: http://www.microsoft.com/whdc/winlogo/drvsign/best_practices.mspx