Open the windows and doors. High humidity is often caused by a hyperventilation or poor air circulation. Opening a window or door will change this.
Turn down the heat. Keeping your home cooler will reduce the temperature difference between the air and the glass. Try to keep the temperature between 66 to 68 degrees.
Minimize your cooking times and turn on a fan when cooking.
Turn on the exhaust fan in your bathroom when showering and take shorter showers with cooler water.
Check that your clothes dryer is properly vented to the outside and not the attic. Try to make the vent ducts as short as possible and seal them with duct tape or caulk to ensure that the moisture leaves the house.
Turn a fan onto the window to evaporate the liquid and put it back into the air. Of course, this will only work as long as the fan is turned on.
Cover windows with plastic or interior storm windows. This will provide a layer between the moist warm air and the cold surface.
Long Term Solutions
Install exhaust fans in your bathrooms, kitchen and laundry room. If possible, install a timer that will keep the fan running for 15 to 20 minutes after you shower to remove any excess moisture.
Invest in a dehumidifier. Dehumidifiers are great additions to bathrooms and basements where humidity levels are highest.
Reduce the number of plants and aquariums in your home—both add water to the air. If possible, water your plants less often.