Check all around your home for any possible pipe leaks. Leaks in your pipes will increase the problem of duct work condensation. Get the leaks fixed as soon as possible.
Find out if you have any moisture problems outside of your home, such as standing water near the foundation or a poorly constructed gutter system. Moisture in these areas will increase condensation in your duct work.
Reduce the overall moisture level in your home, particularly in your basement. This can generally be accomplished with a dehumidifier, which removes moisture and humidity from the air. A dehumidifying system for the entire house might be necessary if you have a serious moisture problem.
Wrap your duct work in foam pipe insulation. This insulation is made to prevent condensation and moisture buildup. Wrap all the duct work you can get to, which is usually located in the basement. Wrapping just a few pieces of duct work can improve the condensation issue throughout your home.