Capturing movment at night

I was just wondering if anyone can give me some pointers on doing a long exposure at night?
I was walking through the park last night and tried to get an 8 second exposure of my girlfriend moving across a light in the ground. The equipment I had at the time was limited to my 80-200 AFS at 2.8 and a fork in the tree as a tripod. Not ideal but worth a try.
We had a ball and want to try again with a proper tripod and a 50mm 1.8 lens. Does anyone have any setup ideas and perhaps some examples of such photography that I could have a squiz at?
I was walking through the park last night and tried to get an 8 second exposure of my girlfriend moving across a light in the ground. The equipment I had at the time was limited to my 80-200 AFS at 2.8 and a fork in the tree as a tripod. Not ideal but worth a try.

We had a ball and want to try again with a proper tripod and a 50mm 1.8 lens. Does anyone have any setup ideas and perhaps some examples of such photography that I could have a squiz at?