Great questions! I think the answer depends a bit on what, how and how much you need to file. Here are some things to think about to help guide you to a solution.
Do you need to store paper? How much? Can you store everything digitally? If so, look at solutions like OneNote or Evernote for your filling needs. The ability to scan and store things digitally could help make you quite a bit.
If you do need to store paper, how much? Would a simple A-Z filing system work? I would get something like this to help you out. https://images-na.ssl-images-amazon.com/images/I/61JdAv1Z0fL._SL1000_.jpg
Go through it periodically and move what is no longer active to a archive set of folders.
I would also keep an index of all the item you put in the file system. You could use GTDNext for that, or a tool like OneNote, Evernote or a simple piece of paper!