Good XML tools abound, but when it comes to creating (authoring) XSD files (XML schemas), things really don't look good.
Most XML editors do the basic: it let you create stuff, with menus for the proper elements. They don't HELP you in any way, though. A few tools have more advanced features, like creating an XSD based on a sample of XMLs.
Now, giving advice on good practice, or offering libraries of sample XSDs with wizards to customize them? I haven't seen it.
So, what do you consider the BEST XML schema authoring tool?