This recent article discussed one of the ways you can use XML provisioning data - through a cab file installation. You can also pass the XML to DMProcessConfigXML or ConfigurationManager.ProcessConfiguration in the managed world. But how about creating the XML?
Well you could use notepad and code it all by hand as a worst-case-scenario. The next best thing is to use the XML support in Visual Studio which will at least help to ensure you write valid XML. Mobile In The Hand takes this one step further by adding a schema into Visual Studio to ensure your document conforms to the msprov schema:-
1. Create a new XML document in your project
2. With the document selected locate "Schemas" in the properties pane.
3. Click "..." to bring up a list of installed schemas
4. Select msprov from the list
5. Start writing your document and watch the intellisense kick in