Freeing up iPhone storage
In iOS, they recently introduced an option to have all your photos saved to the cloud, and have low-quality photos remaining on your phone. If you go into Settings > Photos and select Optimize iPhone Storage, this will happen and a considerable amount of space will be freed.



Another alternative is by an app that you can download. Search for "battery doctor" on the app store. The icon is a green battery with a plug coming out with a silver border.

Here's where it gets weird:


Open the app
Wait for the spinning wheel to go away (located in the top menu bar, next to the WiFi indicator)
Double tap in the blank bottom area (above the bottom menu, but below the top header)
Quit the app via the app switcher
Open the app again, if it looks different, you're good. If not, go back to step 2.
Go to the bottom menu item labeled "Junk"
Clear your cached files.


As always, I recommend backing up before you do this. I was able to clean >1 GB this way, results may vary.