The biggest cause of a blurry or "unsharp" photo is too slow shutter speed. As a general rule, your shutter speed should be the same as your focal length. For example, if using a 50mm lens your shutter speed should be at least 1/50th of a second. For a 100mm lens it should be 1/100th of a second.
This rule applies to a full frame sensored camera.
For a cropped sensor camera you need to multiply the full frame equivalent crop factor by the focal length. For example; in a APS-C cropped camera with a full frame equivalent of 1.5, a 50mm lens should require a shutter speed of 1/75th of a second (50 X 1.5). For a Micro 4/3rd camera the factor is 2X (50mm = 1/100th sec shutter speed).
Again, this is for general shooting. If you or the subject (or both) are moving you need to increase the shutter speed more.
For Dark Rides I generally look to shoot at 2X the focal length. The following shot was taken with at 55mm lens @ 1/100th of a second on a full frame camera (f/1.8, iso 6400).
Other factors that could effect this;
how you hold your camera is important. Feet shoulder width, camera close to body and elbows in will create a strong base to keep your camera from moving too much. I try (when I can remember) to press the shutter after I exhale.
Stabilization. Some lenses have stabilization and some camera have sensor stabilization. These are tools the help keep offset natural movements by the photographer. They can generally allow a slower shutter speed, but work best when the subject is not moving. It is not a substitute for holding your camera properly.
When shooting sports or other fast moving objects, shutter speeds have to be much faster if you want to freeze the action. Generally 1/800th or faster.