I would say it very much depends on which computer you're trying to organise.
For my work drive, everything is sorted by year then project, and each project starts with a timestamp (= start date), so:
2014/
2014_01_Project A/
2014_03_Project B/
etc.
and on top of this there's an admin folder to sort contracts etc.
For my personal computer, I tend to organise things by file type (apart from personal projects which are organised as per above), so one folder for videos / images / audio / documents, and then I tag the file accordingly (using the Mac OS X tagging feature).
For my work drive, everything is sorted by year then project, and each project starts with a timestamp (= start date), so: 2014/ 2014_01_Project A/ 2014_03_Project B/ etc. and on top of this there's an admin folder to sort contracts etc.
For my personal computer, I tend to organise things by file type (apart from personal projects which are organised as per above), so one folder for videos / images / audio / documents, and then I tag the file accordingly (using the Mac OS X tagging feature).
Hope this helps!