Plain old HTML would work, or you could do a DSP hosted on the IS server (explained in the DSPandTemplatesDevGuide.pdf)
Here’s the plain old HTML way:
You would need to create an HTML page with a FORM element. The FORM start tag would have the attributes action= and method=post. Between the start tag and the end tag would be the INPUT elements you want to use to retrieve the values.
For example,
Of course, you can make it prettier than that, but there are other forums for HTML authoring… 
#webMethods#webmethods-Protocol-and-Transport#Integration-Server-and-ESB