It is quite amazing, really, that not every Android handset comes with a file manager as standard. There are lots you can get from the Play store, though, and plenty of free options. I've used a large number of file manager apps in the past, and now I am using Tomi File Manager. There are two great things about this app: Firstly, it's very visual user interface, and secondly how easy it makes file management.
Tomi File Manager automatically identifies video, music, pictures, apps, docs and downloads. That last group can include email attachments and other bits and pieces that just clutter your memory up without you realising it. The main screen tells you how much of your storage space downloads are cumulatively consuming.
Tap a file type on the app's main screen and you are shown a detailed listing of each file. Tap a file to access it – view documents, listen to music, watch video and so on. Long press a file to copy, move, delete, rename or share it. Also, all it takes is a single press of the Apps icon to list all the apps you have installed. From there it is simple and quick to remove any you no longer need. Brilliant!
Product: Tomi File Manager