The document discusses supported techniques for customizing SharePoint, including using custom site definitions to control default features and content, modifying copies of files rather than the original files, using CustomAction entries to redirect links, and using delegate controls to override which user controls are loaded. It provides examples of customizing administration interfaces and lists other potential customizations like the content query web part and publishing console. The key message is to avoid direct modification of files and instead use SharePoint's extensible architecture through these supported techniques.