There are companies, listed in the phone directory, who specialize in this process. It really cannot be done by the homeowner since it requires special equipment.
The research we have done on the matter basically agrees with DrHome, with a few additions. For one, having the ducts cleaned out after the house is built (or remodeled) will reduce the initial debris being blown about the home, but gradually, everything that can blow around the home will, and the heavier stuff won‚Äôt.
After that, it seems to be a good idea to clean out the ducts when you buy a used home, like in our situation. As you live in your home, it becomes full of your family‚Äôs germs, skin particles, etc., etc., but that‚Äôs okay because you become sort of immune to your environment, or at least tolerant. When you buy someone else‚Äôs home, you inherit, for at least a short time, some other family‚Äôs germ pool. Cleaning things like ducts and carpet go along way to help with that transition.
Beyond that, the articles seem to be somewhat divided on regular cleaning. I tend to agree with DrHome and those articles that do not believe additional cleaning is necessary. But to make sure you understand all points, the side that recommends a regular cleaning (3-5 years) do so because they believe germs and viruses can manifest themselves and thrive in ductwork full of particles of debris, particularly in a warm, moist environment like what can be found in forced air heat with a whole-house humidifier.
For the record, I removed the whole-house humidifier in favor of room versions. We are also looking at various filtration units for our heater since studies we have read show a dramatic improvement in air quality. At $300, the unit we are considering is only $25 more than the ductwork cleaning service.