Here's a consolidated list of my top 10. This post will be updated as I go through the series…

Best Practice 1: Only use SharePoint designer to brand SharePoint sites when the scope of the customizations will never need to grow beyond a single site collection.

Best Practice 2: Use a custom master page deployed via a feature on all your sites to extend your company's brand across an entire farm.

Best Practice 3: If consistency is important; don't let end users toggle the themes on their SharePoint sites.

Best Practice 4: Never make changes directly to the 12 Hive on the file system.

Best Practice 5: Make sure all 12 Hive customizations are in source control in a way that requires developers to use it.

Best Practice 6: Use SharePoint Solution Packages to enforce consistency across all the web front ends in the farm

Best Practice 7:

Best Practice 8:

Best Practice 9:

Best Practice 10: