Tips posted by dcasper
Use external shutter release when shooting with tripod
If you are taking a picture with a camera mounted on a tripod, you should use the external shutter release (cable or infrared) rather than the shutter release button of the camera itself.
The shutter is opened once the button is pressed, and the release of the button will usually cause the camera to move a bit, making your image less sharp.
Taking sharp images without a tripod
When you take pictures with long exposure (anything longer than 1/50 sec) you will get a blurry image unless you are using a tripod. But what if you don't have a tripod around?
One solution is to find something to lay the camera on while shooting. Another (although not as good) is to hold it in hands, but fixate the hands on something, for example a window ledge.