First stop normally is a blower (A Gitzo rocket is HIGHLY recommended). Nossel near the mirror box, but not in it)
Work left to right, and going back to the left and starting again.
Do this in a clean enviorment.
When it comes to a wet clean, I prefer to send it to a pro cleaner (My 20D and 300D tend to go off toghether when I'm in London for a day trip for a clean out. (I use a company in London called "Fixation"
http://www.fixationuk.com. Costs £25+VAT.
There are lots of solutions out there (hovers, spinners, brushes) ... but if you're NOT confident (like me), PLEASE DON'T DO IT YOURSELF. YOU DO RUN THE RISK OF PERMENANTLY DAMAGING YOUR CAMERA!!!!
Nikon will service their cameras within the warranty period at a Nikon service point depending on workload.. Canon would charge £60 or so.
Be warned that if you have an anti dust solution on your camera, it still wont' deal with ALL of the dirt, so account some time for cleaning for your camera.