I love shooting at night. It's fun to watch colors come out that you can only barely (if at all) see with your eyes — humans see mostly black-and-white in the dark. Here are a couple different goals I aim for when shooting in the dark.
The moon looks awesome. I often challenge myself to incorporate the moon into my nighttime compositions, and it's extra rewarding for me when I can find some way to capture the moon's texture:
Moon through a leaf: http://xsdg.zenfolio.com/p326146770/hfeb841d
Bell backlit by the moon: http://xsdg.zenfolio.com/p277017626/h3066979f
Tall grasses at night: http://xsdg.zenfolio.com/p277017626/h93e856
Beyond that, I'm a big fan of spectral hilights and other bright spots of light in an otherwise gloomy image.
Stars from last night: http://xsdg.zenfolio.com/p277017626/h1b06f0cf
Contemporary Jewish Museum, SF, CA: http://xsdg.zenfolio.com/p277017626/hf4a947c
Finally, don't be afraid to shoot moving things at night! Sometimes you get lucky, other times you just figure out ways to make the photo work.
Bike race by night: http://xsdg.zenfolio.com/p277017626/h14e28cd6
Street photography in NYC: http://xsdg.zenfolio.com/p277017626/h34e554e0
I think my most valuable advice would be to try things, even if you're convinced they won't work. Luck might land in your favor, you might learn how to accomplish your goal, or you might learn a lesson that will take you in a different but interesting direction.
Cheers,
--xsdg