Dropped your phone in water?place it in a bag of rice(uncooked) for 12 hours, the rice will absorb the moisture and if you're lucky enough your phone might work the next morning.
An alternate for rice in the above hack is silicon bags that you find in new handbags, suitcases and stuff.
Don't throw them away.Save them for a rainy day.
If your phone freezes,plug it into the charger. This will free it up again .