Wash your hands before you play and wipe down the strings and fretboard afterwards.
Buy a temperature/humidity guage and see what the readings are for your house.
If it's over 50% humidity for an extended period of time, get a humidifier.
Generally during winter it should be about 25 - 30% (more like 20 - 25 if you have electric heat) During summer it'll probably be in the 40 - 50% range.
Try to keep the heat at 72 - 75 deg.