Singlespeed & Fixed Gear - SS MTBing, advice?

Now that I have my fixie together my MTB got re-masculated and got it's fat tires put back on. I also swapped gears around and I'm sitting pretty with a 32-17 no tensioner needed. Pretty happy with the bike.
So now it's time to take it out. Can't do it this weekend, can't do it during the day, so I have to do it at night, on trails that I've only hiked before. The good news is that they are pretty wide and smooth and there isn't really any elevation to speak of.
Any adivce on how not to hurt myself tonight? I've got a pretty good headlamp and it worked really good for riding around in the trees behind my house last night so I think I'm cool with that. Just haven't been on dirt in quite a while, never on a SS and never in the dark.

heres my advice: be careful. although the 32-17 w/ no tensioner may seem like its perfect, ive been there. i had a 32-16 on a bike with vertical dropouts and i thought the tension was perfect, but when i applied enought torque while climbing a steep grade, it would sometimes skip a tooth. i ditched that frame for an old specialized with semi-horizontal short dropouts. in the long run you should look for a different frame , or get a tensioner just in case!

Thanks for the advice, but really, it's not a problem, the dropouts have about 3/8ths of an inch of play in them and it all works out well. I can fine tune the tension on this bike as well as I can on my fixie. Really, it'll be good. :)
Now about riding in the dark.......

Now about riding in the dark.......
-Ride familiar trails, they won't look that familiar at night.
-Lots of leaf cover? Keep an eye on the trail or you'll lose it easy at night.
-If you are only running one light, take a mini flashlight in case you need a backup.
-Don't believe manufacturers burn times, plan on less. Even better, do a test burn at home, but beware that cold weather can shorten burn time.
- Ride w/ a buddy if possible
- Don't use an underpowered light, those little commuter jobs don't work well on the trail

Have fun, you'll be hooked!

And carry some sort of emergency backup light with you! I carry a $15.00 Energizer dual LED headlamp that I picked up at Target. Elastic headband "spelunking" type of light. Provides JUST enough light to ride slowly, not on technical terrain - JUST IN CASE something happens to my main lights.

It even has a RED LED you can use to maintain your night vision if you need to do that for some reason...

http://www.sierrasurplus.com/energizerled.html

http://www.sierrasurplus.com/energizerled.jpg

Bloody hell that was fun. I couldn't ride fast enough to really even work up a sweat but it was really cool. The big problem is that if I'm looking far enough ahead to go a little bit quick then I'm skipping over seeing the small stuff right in front of my wheel. Just about need ESP. I also got out into a field that was completely fogged over and I could only see about a bike length ahead, that was exciting. I really enjoyed it. Bike worked great, had a good time. I'll have to do it more. :)

The best set up is a handlebar light aimed for the stuff right in front of your wheel and a helmet light aimed a bit further.

What type of light are you using? A single 10w is the bare minimum for the trail if you want to keep a decent pace.

I'm using an older Petzl duo. For some reason I think the big bulb is 10W but maybe not. It's not really total output as much as beam pattern. I have to focus the beam as tight as it will go to get the detail I want but that gives me sort of tunnel vision.
The ability to switch to the small bulb was really nice when I got into the fog, I could actually see better with less light. I also really like having a spare light with just the flip of a switch.
I like your suggestion to use a bike mounted light too and I'm thinking that would really help me out. Maybe for christmas.