Mine are constantly dusty, the really only way to clean them out is with compressed air. I know some people use vacuums but I also read that can cause static and really screw up your laptop.

Id say just pop off the upgrade bay on the bottom and blow it out the best you can. Heres a video of someone cleaning out their G73's vents similar to our g74's. http://www.youtube.com/watch?v=EQ9g5WKHWJA