if you have a light on your handgun you may want to consider using the same light.
If you go incandescent i would suggest a 6v (60 lumen) light, its bright enough for nightime use outdoors to 25 yards and indoor without blinding you when you light up a mirror or tv screen. a 9volt light is good if you want to clear a large building or for use outdoors. Get the shock isolated bezel if you can although guys seem to get a lot of shots through plain old 6Ps and Zs without problems.
LEDs seem to illuminate fine for indoor use, i'm just waiting for them to be out longer before i trust them.
No tape switches as they are extra parts, can't be locked on (if you aren't into the flash dance thing) and are too easy to inadvertantly activate. Make sure that you can activate the switch without drastic changes to your shooting grip while ensuring that it has to be a conscious decision.
A tritium front sight can be a nice thing.
If you get an opportunity to practice at night, preferbly under instruction, then take it.
my $.02.