Running out of space? Want to know where all your space has gone?
To see how much space you have on your phone, and how much of that is available free space goto Settings -> Usage. You'll be greeted with a spinning wheel while the device does calculations to see where all of your space is being used. Also on screen is a number labeled "available" and a number labeled "capacity". Capacity is the total memory in your phone. I have a 32 GB phone and after formatting, system files, etc. you'll see that I show a capacity of 26.8 GB. My available space is 743 MB. (There are approx. 1000 MB in a GB.)
Once the device is done calculating the specifics on storage space, there is a nice list of applications along with how much space each is consuming. The measurement you see on the first screen is the total amount of space the app consumes, but tap on the app to get more details. In the screenshot you can see that I have Instacast downloaded. The app itself is only 9.7 MB in size, however the app has 1.8 GB in documents or data. For this app it's all audio and video podcast files. With other apps, such as Facebook this would be cached data the app has downloaded so that it can load faster, settings saved locally on the device, etc. Some apps have "Clear Cache" functions, such as Instacast, that allow you to clear out all the locally stored data. Other apps will have to be deleted and reinstalled to clear their cache.
Messages is another offender on my list. To remove the data used here, each conversation will have to be deleted one-by-one. Hopefully Apple will make this process easier in the future!
Lastly, if tap Music or Videos you'll see that it shows details on the videos that are downloaded to the device. There is a handy Edit button in the top right corner that allows for quick deletion of unwanted media.
If you're running of of space, this is a great place to start to recover it!
This tip works for all iOS devices running iOS 7.