Shooting in the dark, without knowing where exactly to focus, can be quite a task. Shooting aimlessly would be a possible solution, but you might end up with a few dozen goofed-up pictures, especially when it involves taking portraits. Using the auto focus mode is literally of no use in the dark, for there is no light that will guide you towards your object.
Using manual mode is the best solution to lock the focus into the frame. Low light photography, and night photography is all about trusting your instincts to get the best out of the little illumination available. Keeping the shutter open for as long as possible is the only way to ensure a quality picture.
Remember, night photography or low light photography is about depth and dimension. It would be beneficial to avoid using the flash constantly, and ruin the photograph.
The main reason to do this is because firstly, there is hardly any light for your lens to find what you want to set your focus on. And secondly, finding your focus in manual mode is relatively easier. Do remember to change the settings to manual mode, to avoid kicking the camera into auto focus at the wrong moment by accidentally pressing the shutter button.
Press the shutter half-way to flicker the flash, thus illuminating the subject enough for you to focus. Remember to change the setting back to manual mode and turn off the flash, and click the perfect picture.
If you are planning to photograph the beauty of the night sky, it would be wise to use this setting, as it can automatically focus on bright objects like planets and stars.
Once you set your focus, do remember to switch off the flash light. If need be, you can focus on your subject from a distance, thus throwing light on the subject to lend a different dimension to the picture.
Using an Infrared Beam
The IR assist beam in an autofocus camera switches on for a couple of seconds, allowing you to focus, and then switches off automatically, when your focus is fixed. Remember to purchase one for yourself, and to keep it handy in such situations. Hit your subject with the beam of light, and focus on your subject, then turn off the light and shoot your picture.