If your phone is hanging or have any problem then you can reset your phone by pressing some master keys.
1. Turn the power off
2. Press and hold the Power + Volume Down Key + Quick Button
3. When the LG logo appear, then release all keys, all data will be lost.
you will lost all data with applications, so before reset your phone, don't forget to take back-up in SD card. You can also save contact as Vcard in SD card so that you can restore later.
If you still have problem in your phone then you can contact to LG customer care.