Here's how: 1  Stand with your feet shoulder-width apart and knees bent slightly. 2  Lean forward, placing your hands just above your knees. 3  Round your back so that your chest is closed and your shoulders are curved forward.  Then arch your back so that your chest opens and your shoulders roll 1  back. Repeat several times.
Typically this count is between 100,000 and 300,000 shutter actuations, with the latter limit associated with the EOS-1D models. In fact, the Camera Shutter Life Expectancy Database is a really neat user-based site for DSLR models of several brands, including Canon.
If you are looking into buying a camera with a lower shutter rating, say 20,000, make sure that you understand how you intend to use it. I bought my first camera ever, a Canon Rebel XSi (450D) about 18 months ago. I burned through 5000 shots in the first two months with it, and have over 10,000 shots on it so far. I expect this body to last me at least a few years, and if it only had a rating of 20,000 shutter actuations, it would probably be done by the end of this year.