In this way your mobile data can fly, then back it up somewhere and keep the memory card apart.
1. First switch off your smartphone
2. After that
If you have a mobile of Micromax, Lava and Intex, then press Volume + and Volume- and power buttons together after switch off and
If Samsung has a phone, press Volume + Power and Home button together
3. From this select the option of Wipe data / factory reset, select option from Power button or Home or volume button
4. Yes delete all user data option
5. After that choose the option of Reboot and just the lock of your phone is open.