The best thing anyone can do for their carpet, well actually it's a "two-step" process, is using door mats! That's right, a rugged outdoor mat at all your outside entries to get the major dirt, and debris off. Then use an absorbent inside mat to remove unwanted moisture and lighter "dust" particles.
The outside mats should be able to withstand the elements and have someplace for the dirt to drop into so that it doesn't get contaminated and start doing the opposite of what it was intended to do.
The inside mats should be heavy enough to lay flat and have a rubberized back to prevent creeping. These mats should be small and light enough to be able to be washed in your home washing machine.
Kitchens are another great place to have mats to prevent cooking oils and food-stuffs from being tracked into the carpeted area of your home.
Although it's probably not a good idea to put them in the dryer, remember to clean these mats often as they are the heart of prevention.