I start by making sure I arrive at my shooting location at least an hour and a half before sunrise or an hour before sunset. This gives me plenty of time to get set up and to determine the location I think is best suited for night shots. This is important because the window of opportunity to capture the brilliant dark blue sky is quite short. I typically find that I only have about 10 - 15 minutes to shoot the background I love. Because you are using long exposures, this greatly limits the number of shots you can capture. As such, being all set to capture the shot when the sky first hits the right shade is critical.
I consider a perfect location to be a spot where I am looking at a well lit cityscape or a building across water. I like to get as close to water level as possible and shoot from a low perspective. This will stretch the reflections of light. I shoot in manual and use a small or large enough aperture to allow me to get to a 30 second exposure while leaving me 1 stop overexposed. As the sky gets lighter or darker (depending on whether I am shooting dawn or dusk), I adjust the aperture t0 remain at 30 seconds. I like the longer exposure time as it smooths out the water and adds the starburst effect to any street lights. Because I am shooting large expanses of dark sky, it is critical that I shoot in the lowest ISO setting my camera offers. The difference between ISO 100 and 200 on my Nikon D300 is HUGE in terms of the noise levels in the sky.
I aim to get as many shots off as I can within the 10 - 15 minutes of brilliantly blue sky so I tend to find one composition I like and lock down my tripod. This obviously limits my variety of shots but I have found that I am far more likely to get the beautiful shot I have invisioned.
Post production is a key part of my night shots. I only shoot raw so I have the flexibility to adjust exosure and white balance after the fact. I capture versions of each image correctly exposed, overexposed by 1, 2, and 3 stops, and then underexposed by 1, 2, and 3 stops. I use Photomatix Pro to create a High Dynamic Range image using those seven files to bring out the bright colors in the buildings while maintaining the dark sky (limits noise) and not overexposing the street lights (avoids blooming). I try to limit the adjustments I make in Photomatix in order to maintain a "realistic" look to my image and to decrease my chances of adding an unacceptable level of artifacting (a big no-no in stock photography). Once I have my HDR image, I export the file in TIFF format and move to Photoshop for any clean-up work (like the painstaking process of removing the names off buildings in cityscapes). Once the file is cleaned, it is ready to be exported to JPEG and uploaded to my favorite stock site.
Below are some examples of night cityscapes taken using the above process. From top to bottom, they are of Richmond, Richmond, Baltimore, Tampa, and the Capitol Building in Washington DC.
