Althought repairing the damage is the only way to prevent it from growing, here are a few things that may keep your rock chip or windshield crack from expanding before we can fix it.
Do not park on a steep driveway or hill
Parking on an incline may lead to the damage spreading before it can be repaired.
Do not use your defroster or air conditioner on the glass.
If you rapidly heat or cool your windshield, it may cause the damage to spread.
Do not wash the car or get the glass wet.
Refrain from washing or exposing the glass to rain to prevent further damage. Sealing the crack with packing tape is recommended if the glass is exposed to rainy weather.
Do not add anything to the damage.
Do not apply any substances to the damage. The only effective way to strengthen or prevent the spread of a chip or crack is to have it professionally repaired. The use of super glue, nail polish, or any other adhesive will hinder the success of a proper repair.
Cover the damage with packing tape or something similar.
Use packing tape to cover the damage and keep it dry and clean. Although this won't prevent the damage from expanding, it will increase the likelihood of the repair looking its best.