Use a Cable Release
With slower shutter speeds at night a tripod will usually be required to get a sharp photo.
Another way to help is to use a cable release rather than pressing the trigger manually. A basic cable release can be purchased inexpensively (either made by your camera’s manufacturer or a third party) and will allow you to get the sharpest photos possible without needing to resort to using the auto timer to avoid any shaking.
A cable release is also necessary if you will be shooting longer exposures in bulb mode (more on that later). Manually holding down a button to keep the shutter open in bulb mode is not a realistic option.
Know Your Camera’s ISO Capabilities
The ISO setting will obviously impact the shutter speed you can use at night. Most cameras will use a very high ISO at night on auto mode in order to avoid very slow shutter speeds.
In general, you’ll want to keep ISO low to avoid graininess, but many modern cameras, especially full-frame DSLRs, are now handling higher ISOs extremely well. Because of this, it is key to know your camera’s capabilities in relation to ISO. Take plenty of test shots at varying ISOs and examine them at 100% to see when the noise becomes an issue. When shooting at night be sure that you are keeping the ISO in a range that allows your camera to perform well.
Bracketing exposures can be helpful for blending multiple exposures and for HDR processing. This can help you to get a better dynamic range while shooting at night. Bracketing can also help simply be ensuring that you don’t over or under expose the photo, since you will have several different exposures from which you can choose the best.
Most cameras have exposure bracketing built in, which makes it very easy. For more see this guide to exposure bracketing.