How can I pre-populate the Wiki text editor with some default text, so everytime I press the 'Create New Page' button that text appears automatically in the text editor?
Copy the site-webscripts/org/alfresco/components/wiki/createform.get.html.ftl file into the tomcat/shared/classes/alfresco/web-extensions folder, maintaining the folder structure.
Then insert your copy between the <textarea></textarea> tags. TinyMCE should pick this content up upon initialisation.