What are other ways to save iPhone storage?

I have deleted all of the apps that I don't use and deleted all my mail and photos I don't want but I'm still lacking storage

Could try clearing cache memory. Phone Clean is a desktop app you could try to do that.

First you should see space used by going to Settings>General>about, this will show available space.
If you have time then follow some below steps:
1.Delete the watched videos or tv series; Setting, general, usage slide left and click delete. You can put your iTune series in computer for future.
2.Try to del apps that occupying mostly
3.Save images in your msgs-in message-select one and save to camera roll do it for necessary ones
4.Delete all messages, mms, imessages
5.You should delet photo steam by Settings -> Photos & Camera -> My Photo Stream -> Delete.
6.You should data safari cache, reminders, notes stocks etc