1- Charge Micromax Q391 upto 70 percent.
2- Switch off device.
3- Press & Hold Power and Volume UP key.
4- As soon as Micromax appears, release power key and hold Volume up key only.
5- Choose Wipe Data/Factory reset using Volume keys and power to confirm.
6- Select Yes-delete all user data.
7- Reboot system now using power key.