Just don't even begin to worry about cleaning the sensor in your camera - it's really easy. Well, you're not really cleaning the sensor itself, simply cleaning dust off the glass in front of the sensor. Lehmans (a company recommended earlier) market a number of sensor cleaning devices with full instructions so no point in paying them, or Canon, £25 when you can do it yourself in 2 minutes flat (incidentally, Canon service centres in several other countries do this job for free). I've done it a good number of times in the past but my "L" lenses have a rubber gasket which presumably provides a more effective seal than my other lenses and dust has not been such a problem lately. I apply all of the tips above, even the "switching off" bit, although this has been effectively argued as unneccessary by techies elsewhere..