I've tried to clear storage on my phone by going to "settings", "more", "storage". There is a colored bar that shows the amount of space taken by such things as apps, pictures, etc. The most space seems to be taken from Miscellaneous Files. I then click that in the list and select all to delete them. However, the system memory is still there taking up 6.26gb. I also clear the cache from this screen. The remaining space is then 1.28gb. These are basically the steps I already found here for "Check Memory". Was wondering if there is another way to clear any more space (like the system memory)? I'm not sure what that could specifically be and how to get rid of it.
Also, would it just be a better idea to use a memory card? If so, what size would be best? Is it easy to transfer certain things to the card or would everything be saved to the card? What a bother...
With the age of the phone, it may be time for an upgrade. In the meantime:
clear system cache:
The S4 supports up to a 64-GB micro SD card; to move files to the card: