1- Turn on your airplane mode.
2- If you are waiting for any important calls or messages then ignore step one and simply turn off any unused feature like wifi and bluetooth.
3-Atleast once in a month charge your mobile from 20% to 100% this enchances battery life.
4- Atleast once in a week restart your mobile or switchoff the phone for 5 mins remove battery and reinstall and reboot.
5-The most effective is that buy a charger of a mobile like note 3 coz it charges faster than normal grand 2 charger(use at your own risk)
6- If you feel your mobile is getting hotter while charging turn off power saving mode if issue still remains turn off the phone.