FOR MICROMAX A75 DEVICE:
Requirements:
1. Drivers installed on system, both specific drivers n ADB drivers (here)
2. Unsecured boot.img: here (Credits- me)
3. UnlockRoot: here (Credits- Respective developer)
You may also try SuperOneClick if u prefer it.I used UnlockRoot.
Method:
1. Flash downloaded modded boot.img to device.
- U must know by the time how to flash A75 using SPFlashTool (See Here for Info or here)
- Put newer boot.img replacing existing one
- Tick only BOOT (boot.img)
- Download
- Let it finish.
2. Power on device.