This is a dead simple tip that applies to all sorts of photography. Want a steady shot? Use a tripod! When shooting at low shutter speeds, tripods are extremely important. Remember that the goal of leaving the shutter open is to capture a great deal of light in one photograph. If you're shooting a busy highway, the lights from passing cars will blur together into cool light trails. But if you're shooting with a camera in hand, the picture probably won't come out very well.
Why? Because the photograph will be affected by every subtle jitter of your hand. Even depressing the shutter button will create movement. Steady hands or not, it's difficult to hold a camera still without introducing blur into the picture. Solution: Place the camera on a tripod. Then the only motion you'll capture is what's in front of the camera