We defined naming conventions for files and folders, then trained the team to use them. For ongoing monitoring, we have admins who periodically check for conformity. Our approach is to work to prevent bad habits from forming.
I set up the naming conventions for programs and campaigns first, then train. During the training I constantly emphasize the importance of naming convention because it's easier to associate files or find them when the naming convention is consistent. I do monitor everything and I haven't had to send a friendly reminder.
Also a big help to me is only use templates that are associated with your department. For instance for Events, there's always an "Event" on the naming convention so they're not using the Marketing templates or Editorial or sponsorship templates. All images, landing pages and other files in Design Studio have their own department folder, and all departments should drop or access files from their own folders.
Any templates in design studio that I don't want anyone messing around with, I store in a folder called "Do not touch".
Constant enforcement and monitoring!
And heavy training.
@ Josh: this is what we are currently doing and this is taking a lot of energy
@ Mike and Michelle: lucky you! in our case, we have users who just do something wrong, keep cloning it and then it's domino effect... and I'm not talking about those who are doing typos because they have forgotten to put their long-sighted glasses!