Typically it is apps on the phone itself, and Google is horrible about taking up a large chunk of space with all of its updates. First go into the Google Play phone and disable automatic updating. Second would be to go into device apps to remove the alternate Google apps you rarely/never use like hangouts, music, movies & TV, and so on. Many of these can actually use up a lot more space since it copies the same user data among the different apps taking up a lot more space than it should. The photos and movies are almost always on the SD card so you can keep those where they are, but also check the internal storage to see if some got saved to the phone, and move those to the SD card. I've found Android (System) itself typically uses...