In my view there are two key elements to consider as a photographer when aiming to capture scenes of any city during the night, the first one is that you will not only play with the light (artificial), but also with the lack of it (darkness and shadows). The second one is to always consider the type of photography or concept you want to explore. If you seek active night life pictures of people interacting, then certain days will offer more opportunities than others, as well as the size and spirit of a city will also make a difference. If you seek quietness, then certain hours and parts of the city will offer you chances to capture that.
Cities at night, specially capital ones or the most crowded ones, offer a great opportunity to photograph them with less human presence, interaction and movement. This can give you opportunities to photograph iconic buildings, places without the presence of tourists or the daily crowds in busy business districts, being able to explore and perceive the city with a different look.
City lights may come from isolated street lamps, to overexposed illuminated monuments, but it is important to be aware that this type of light functions and behaves in a very different manner from the natural sun light. Artificial lights at any city is normally more directional and hard, which has a direct impact on what is seen and not on the photographed subjects, as well as it usually comes from small focal that should be photographed in specific ways to prevent or add certain visible effects in the photographies.
There are also different colourful light sources in the city that can offer very unique opportunities for creativity and experiment. Specially when combining movement and lights, it can create very great effects when playing with slow shutter speeds.
In general for night photography, depending on how much experience you have with the camera, you may need more time to adjust parameters, as conditions of light may change massively from one street to another. As it is eventually another type of urban photography, you never know what you may find, so using an automatic or semiautomatic mode may also facilitate the work.
Tripods, and the use of fixed focal lens could help you to get better quality pictures. Tripods are a must if you plan to get clear and deep depth pictures in dark conditions, as you require them to work in slow shutter speed conditions. Fixed focal lenses present broader apertures which enables more light to go through the lens, thus it will also allow you to get clear pictures even in low light conditions.