How to hold the Camera ?
The most vital thing about holding the camera is that you should be as stable as possible. Grip the camera firmly and release the shutter gently rather than with a jerk. Hold your breath as you click especially when shooting with very slow shutter speeds. Just ensure that you are not shaking the camera as you breath. Take support where ever possible and keep the centre of gravity closest to your body. If your frame is kind of fixed you may also opt to use a tripod while shooting at slower shutter speeds. Alternatively for more flexibility you may increase the ISO so that your shutter speed does not drop down. With the tripod you loose quick flexibility in framing your shot and it does not take care of the subject movement and with higher ISO, you do get relatively higher shutter speeds and can thus take care of the subject movement as well but at the cost of higher noise in the photograph.
How to Hold the Camera -1
How to hold the Camera 2