If you get into the habit of tagging each shared file, then you will automatically organize your files in an intuitive way that groups them by theme. This will make future searches much easier.

Make sure you use simple, generic tags: ‘Holidays’, ‘Christmas 2007', ‘John's Birthday' and so on, and you won't have any trouble organizing your files.

Tip: if you tag each photo or video with the names of the people shown, you will be able to build up albums for each of them.