I'm dogmatic - if there is a 'right' way to do something, I want to do it (or at least learn how to do it) the 'right' way.
So often, I've seen

[xml]$xml = "<xml />";

That's one way to do it, but not the RIGHT way, dammit.  I want to use the constructor:

$xmlDocument = New-Object System.Xml.XmlDocument;
$ivaultsNode = $xmlDocument.CreateElement("xml");
Then we do stuff such as:

$fileNode = $xmlDocument.CreateElement("file");
$null = $fileNode.SetAttribute("name", $file);
$null = $xmlDocument.AppendChild($fileNode);

And finally we close with:

$null = $xmlDocument.AppendChild($ivaultsNode);