As much as we love our Android devices, sometimes things go wrong and you end up with a frozen or blank screen. So what can you do about it? Well different manufacturers have different ways of going about it, but here are three different ways to force your Android device to reboot:
Note: Before attempting any of these, you should try to find instructions for your specific device
1 – Simply hold down the power button for about twenty seconds. This method almost always works and I have yet to find an Android device on which this method doesn’t work as a whole, but just in case this method doesn’t work in your specific case, move on to method number 2.
2 – Hold down a combination of the power button and one of the volume keys (usually the volume down key) for about 10 seconds. It’s   important that once the phone begins to reboot, you let go if both the buttons you pressed. Holding the power button longer will cause your device to continuously reboot until you let go. Holding down just one of the volume buttons could bring you to some alternate modes, such as download mode or recovery mode. These alternate modes will be covered in future School of Android posts.
3 – If neither of the above methods worked for you, and your device has a removable battery, then as a last resort you could simply take out the battery, then re-insert it. This method should be used as a last resort as many manufacturers warm that this could potentially cause damage if the device was performing an important operation.
If none of these worked for you, you most likely have a bigger problem than a simple glitch and you might need to start looking into problems for your specific device online, or the cost of repairs if your search comes up empty.