Get a bright blinking tail light too of course. My ideal setup is a medium-powered light on the bars to avoid potholes and debris, and the main, brighter light on my helmet. When I look at cars, they see me, when I'm cornering at high speed I can see where I'm going instead of where my bars are pointed, etc. When I look at something, I see it.

I'm WAY more visible in pitch darkness than I am at any other time cause of the contrast. Just consider the chance of there being more drunks out driving around.

Tons of fun.