The first option we have is to delete the last video, photo, or last thing you have done on the camera. It is important to remember to be careful, for example if you have taken a burst set of photos, if you select delete last photo it will delete the whole burst photo not just the last photo from that burst.
We are going to go down to All/Format using the mode button
It is very much recommended to format your camera and SD card on a regular basis. This is because reformatting the SD card returns it to the original file system allowing it to properly communicate with the camera for future use.