[font color=\'#000000\']The easiest way to tell if you have dust on your sensor is to take a picture of a photographic gray or white card. Those dust bunnies will be obvious.
I have a Giotto Rocket for blowing dust off the sensor. When that does not do the trick, I take the camera into Cam-Tek in Tampa. He's a camera repair technician. He uses a microscope and a micro-vacuum to remove any dust, pollen, etc. It costs me $25.
You cannot really touch the sensor. It is behind the low-pass filter. Still, I'm risk-adverse about touching that. So, I would rather pay $25 to have it cleaned when a blast of air from the Giotto Rocket is not sufficient. So far, I've only had one DSLR cleaned (out of three).
Most of the dust comes from the rear of your lens. So I keep mine capped until the last second. Then I hold the camera with the lens opening facing the ground, quickly swap the lenses, and immediately recap the second lens. If the car is nearby, I'll do the lens swap inside the car.
Cheers,
Mitch[/font]