To paraphrase Ben Franklin, an ounce of prevention is worth a pound of mucus. So avoid allergens when you can, wash and sanitize your hands to avoid germs, and get your flu shots unless your health history means you can't.
Of course, sickness isn't the only mucus-maker worth avoiding. Airborne irritants caused by cigarettes or bad air quality can bring just as much nasal nastiness as germs or pollen can. Stay well ventilated when working with cleaning products, and try not to walk behind anyone wearing obnoxious body sprays, irritating perfumes or whatever else aggravates your schnozzle.
As for air quality, experts differ on whether the air-quality boost that duct cleanings might (or might not) provide justifies the expense involved. Still, you should keep your furnace air filters clean or change them regularly. You might also consider airing out your house during pleasant breezy days — but only when allergens are dormant [source: Doheny].
Even if you don't get easily congested, you might find that pet dander vexes your sinuses. If so, try bathing your pets every week, setting up pet-free zones in your house and banning fuzzy loved ones (the nonhuman variety at least) from your bed. The heart wants what it wants, but the nose knows better.
And wear a dust mask when you're cleaning or working outside during pollen season. You may feel self-conscious, but keeping the allergens out of your respiratory system will go a long way toward preventing that allergy-sinus chain-reaction.
Sinus Congestion Tips
Here is some information to help you with sinus congestion.