I'd recommend going through
this thread, where we go through a lot of in-depth info on settings for SpectroMagic, including some example photos.
The quick answer based on my experience would be highest ISO you can handle (I did 1600, I might even consider 3200), the fastest lens you can get (I used a 50mm F1.4), exposure compensation for about +1.5 (or +1.3 or +1.6 if you are configured for thirds, not halves) and shutter priority for 1/90th or maybe 1/60th of a second. I took most of my "good" ones in aperture priority but I think I'd have more keepers if I did shutter priority.
And like the others have said, it is really, really difficult to photograph well, especially if you don't want to use a flash. I didn't, for a variety of reasons but especially because I wanted to capture more of what it actually looks like when you're there, and a flash will give you overbright objects in the foreground, and inky blackness in the background. OK, maybe not overbright, especially with a diffuser, but I don't think the photos look at good. Remember that SpectroMagic is mostly lights, and shining a light at a bunch of lights will not give you the same look.