Well, I made many night / low light shoots and, perhaps, I can give you some hints on this.
Because I have strong connections with the Holy Mount Athos, through the years I made many photos at vigils / night services / dark churches aso, like https://vatopaidi.wordpress.com/2011/09/19/spiritual-picture-of-the-day-6/
In fact, there is an entire series of photos, most of them in low light, one per day (except Saturday and Sunday) @ http://is.gd/spiritual_pic
I think that (one of) the most important thing (imho) in the low light photography is the mood
. You should keep the mood. I think that the viewer must know that your scene / subject was in low light because low light influences (sometimes a lot) the characters in your photo.
For example: https://vatopaidi.wordpress.com/2011/09/21/spiritual-picture-of-the-day8/
Also, at least for me, the low light is more powerful than the mundane, day light, allowing to pass much stronger messages to the viewer, like in this one:https://vatopaidi.wordpress.com/2011/09/23/spiritual-picture-of-the-day10/
Yes, I know, sometimes you should comunicate a feeling and/or a happening without leting the viewer know that it is low light. So, you need to be prepared also for these:https://vatopaidi.wordpress.com/2011/09/14/spiritual-picture-of-the-day-
You can also see more examples on the 'Spiritual Picture of the Day' (see the address above) also in the past as well as in the future.
And now the least important part, the technicals:
All were shot with Canon 1Ds Mk II. Usually I shot at 1600 ISO. The camera is old and compared to nowadays standards, isn't very good at it. Sometimes there is enough noise, if you cannot eliminate it without noticing, you should embrace the noise. Sometimes it helps, depending on the photo's message.
Also, you should underexpose your photos with 1/3 till 1 EV or even more. You should be careful to avoid having burned highlights from a powerfull light source which happens to be somewhere near to or in scene. Also, go for the faces and/or strong (body) lines.
- Canon 50mm F1.8 - Cheap, very good. Does the job. Highly recommended. Unfortunatelly at 50 mm it is rather difficult to get environments in tight places (churches etc.)
- Canon 17-40mm L F4 - Workable. F4 is a little bit slow but since we speak about wide lens you can get slow shutter speeds without too much trouble. But beware at distortions and moving subjects (even sometimes this can help you to accomplish your photo message).
- Canon 28mm F2.8 - so, so. Flare prone. Too much flare, especially in churches (candles etc.). Usually I go with 17-40. Yes, I know - one stop wider aperture.
- Canon 28-135mm F3.5-5.6 - (almost) useless. F3.5 at 28 mm - too slow for me. 'nuff said.
Flash? - Well, usually no flash. Very hard light. Disturbs the monks in the churches and that's why I try to avoid it. Also, you must bounce it to have nice results. The churches are one of the worst places to bounce the flash. Very irregular surfaces and painted in many colors. But if you have a simple, normall room with white walls you can use a fill flash at -1/5 or -2 EV with a diffuser on it. And don't forget the gel.
just my2c & hth