I know that somewhere, at some time, in some place I saw mention of how to do reflections in DAZ Studio, but for the life of me I can't find the information again. 

So I turn to the folks in the forum.  I've checked the tutorials here, and at DAZ, and haven't found the answer. How in the world do you get a mirror to work in DAZ Studio, please?

Sorry in advance. I get confused over terminologies.
This thread discusses reflection and has a link to a tutorial:
http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2700580

If you are asking about reflectivity, I don't believe that D|S is capable of that right now. I could be wrong about that, there might be plugins available that can do it. You could ask in the other thread.

D|S can do reflections:
http://www.renderosity.com/mod/gallery/index.php?image_id=1420085&member

Daz does do reflections. 1st of all you need to set a main light source to 'raytrace' and 2nd, you need to set reflections in the advanced portion of the surfaces tab. I don't usually set reflections to 100%, but keep them from 30-80% depending on what I want.

Ok...raytrace...I'll go look for that...
Thanks.

Reflections in Daz are pretty easy, actually.
simply go to the surface tab, select the reflecting surface and set reflection to about 50 ( or whatever you like), select reflection color, refraction, if you like.
Render
That´s it.
I had the problem, that the refelction would not show up, the problem disolved itself, after I did pure software rendering