- Make sure you don't have an sa accounts with blank passwords. This is a really good idea regardless.
- On the sql server, get your .net installation up to .NET Framework 3.5 SP1 or later. Best way to do this is to install Visual Studio 2008 SP1.
- For Server 2003, install Windows Installer v4.5 from the SQL 2008 media. Not needed for Server 2008.
- Make sure that all DBAs, sysadmins, and dev team leads know that they will need to install the SSMS 2008. (Still a good idea if you have SQL 2005 servers in your environment to keep SSMS 2005 and BIDS 2005 installed at your workstation, especially for replication and SSIS packages.)
- Easiest way I can think to do this is to install a SQL 2008 instance, detach/attach the 2005 databases to the new edition. Obviously, this creates a server with a different instance name. This may or may not be a big deal, if you can change your connections strings easily enough.
In all likelihood, you'll instance want to upgrade in-place your SQL 2005 instance. This can be done through the wizard, using the option "Upgrade from SQL Server 2000 or SQL Server 2005."
- Remember that upgraded, attached or copied databases from SQL 2005 may still be in SQL 2005 compatibility mode. Be sure to do your post-implementation testing against databases in SQL 2008 compatibility mode!
Links for more reading:
Clustered environment: http://msdn.microsoft.com/en-us/library/ms191295.aspx