There is the nice IBM Redpaper "The XML Management Interface"  by Rolf Wittich:
It describes the basics, how to access the DataPower XML Management interface and provides quite some samples.
In addition there is a section on troubleshooting.
In developerWorks DataPower Forum  there are often discussions on how to achieve a certain goal.
And sample requests are either requested or provided as part of the answers.
The complete interface is specified in these appliance files:
Today I want to describe a method for easily creating ALL sample requests against XML management interface
by using SoapUI  tool (there are free and Pro editions, the free edition is sufficient here).
First SoapUI does need access to "store:///xml-mgmt.wsdl" and the other files.
In order to not having to download the files I just created a HTTP service on a XI52 box
* listening on port 88
* with Base Directory "store:///"
Now accessing "" is possible.
Next create a new SoapUI project
* provide a name
* reference "xml-mgmt.wsdl" as Initial WSDL
* keep option "Create Requests" selected
* press "OK"
that's it.
This creates new project with "Request 1" under "operation":
This is the Request screen showing some choices:
The management interface provides huge number of choices -- you have to select a single one:
By right-clicking into the request you can save the generated file.
Last, but not least, the generated sample file from our Böblingen lab XI52 box:
Hermann<myXsltBlog/> <myXsltTweets/>