Every device has different way to turn off safe mode. By keeping this thing in mind I decided to share all the possible ways that help you to get rid of this problem:
1. Simpley reboot your device
2. Take battery out of your device
3. Reboot and Press the Back Key
4. Factory reset your device
5. Download Stock ROM and Flash using ODIN
For more detailed information you can check out this guide on [http://www.whatswithtech.com/how-to-remove-exit-safe-mode-samsung-galaxy-s3/|how to turn off safe mode on galaxy s3]