Turn on a dehumidifier in the room that you're painting, several hours before painting begins. Place the dehumidifier in the center of the room and close off the room from the rest of the house if possible. This is especially important if the area has high humidity.
Set the room's temperature through the heating or air conditioning system between 65 and 75 degrees Fahrenheit. This temperature range provides the best conditions for drying paint.
Place box fans around the room set on low after you've painted the walls. Constant air flow helps to dry the paint faster. Open windows if the room has windows. Ensure that when you open the windows, you aren't letting in excessive humidity, high or low temperature or debris that may get stuck in the paint.