Today's tip might at first sound a little dull, and probably more than a little obvious, but don't worry. It's not. Today I'll tell you how to eject a flash drive properly, no matter what.
Every once in a while everybody gets a volume (any sort of media; hard disk, zip disk, thumb drive, etc.) that refuses to unmount (be ejected). And instead of telling you what's wrong, Finder just tells you to "Try quitting applications and try again." And naturally, some of the times, even once you've done all that, you still can't get the thing ejected.
The first thing you'll need to do is fire up your trusty old terminal and type in "sudo lsof." It should ask you for your admin password, which is perfectly normal. The "sudo" command takes your admin password, and grants you superuser privileges for a limited amount of time (superuser meaning you can do whatever you want). "lsof" is an abbreviation for "list open files." Now in a couple seconds, your entire terminal window should be filled with a list of every open file on the entire computer.
With that list in hand, all we need to do next is search for whichever process is accessing your drive, and kill it. In case you haven't noticed yet, in the command line all mounted volumes other than your start-up on are in the folder "volumes" in your root directory. So to search ("Command" "F") for any files being accessed on your flash drive, search "/volumes/"name of volume"". And on the same line as those words, you should find the name of the offending process. Usually "mds."
And lastly, just run the "killall" command I taught you earlier.
Even if you rarely have to go through all that, the wow factor you'll get when you do will more than make up for reading this whole entry. Trust me, I've done it.