Are you considering having duct cleaning done? This is really not a job for you to do on your own. It will take high powered equipment to pull out the debris and dust from within the ducting and that is not likely to be something that you have readily available. Working with a good company will make it worthwhile, though.
Before hiring a duct cleaning company, call on several of them. Find out what type of quote they can give you for your home. They may need to come out to see the home or they may want to know how many square feet are in your home. When they have completed this, compare a few more companies to see which the best price is.