Whenever possible, I use a tripod to secure my camera and lens. A major benefit of using a tripod is to minimize camera shake. Minimizing camera shake opens up the possibility of slower shutter speeds--particularly when the subject is not moving quickly.
For this image of a green-winged macaw, I secured my Nikon D800 camera and my large Nikon 500VR lens to a Wimberley gimbal head and a Gitzo tripod. This, along with some other techniques which I will describe in a moment, allowed me to acquire a sharp image at the relatively slow shutter speed of 1/30th of a second!
In addition to using a tripod and stable gimbal head, I used the following additional techniques to help keep this image sharp:
Let's say that I didn't concern myself with shutter speed and instead just set the shutter speed at 1/500th (since the rule of thumb is to set the shutter speed for 1 over the focal length of the lens to achieve sharp images). At 1/500th, I would have reduced my exposure by about four stops relative to 1/30th. To get those four stops back, I would need to boost my ISO from 640 to 10,000 to maintain the same exposure! Even with the D800, ISO 10,000 is not a pretty sight!