Pretty nice user script for the pre-Visual Editor era (and a problem we'll have to solve in VE land as well), developed by a Hebrew Wikipedia contributor:

https://en.wikipedia.org/wiki/Wikipedia:VPT#Template_Parameter_Wizard

It gives you an autocomplete search box for templates to add in the edit window, renders the template key/value parameters as a form, and apparently has a feature for parameter help/documentation as well. JS code here.

https://en.wikipedia.org/wiki/User:%D7%A7%D7%99%D7%A4%D7%95%D7%93%D7%A0%D7%9...

Something similar has been around in de.wp for a while as well, but at least for plain vanilla template insertion, this one looks a bit cleaner and simpler.