Personally I follow the mantra of "child proofing" before education. Make everything as simple as possible before they even touch the computer. Proper network setup, user restrictions, controlled documents modified by a single user(Makes someone accountable and then people cant change important things willy nilly). Constant backups, blocking potentially malicious domains (Facebook, social networking, Download sites, et al).
The basics though and one of the more important things, is naming conventions. People just assume that if a computer accepts a name its a good one. For example Document,sensor.1.554/TeamBuilding.doc.doc Will cause your computer to *** bricks, and severely mess up whatever backups you've made.
Another good habit to get into is shutting down computers at the end of the work day. Extends the life of the machines by years.
Don't write your password down. If I see a list of passwords written under your key board or monitor I'm taking it. Your monitor or keyboard are now mine.
Report problems immediately. I cant tell you how many times people have popped in and asked "When is the printer up front going to be fixed, I have to print all of this out right now and it hasn't worked in days." Well since no one told me there was an issue nothing has been fixed.
Requiring permission to install software, even if you don't have it enforced through GP or local restrictions its a good habit to get permission to install anything on company hardware. Keeps people from downloading AVG when your running Symantec endpoint, or keeping people from trying to fix "A Slow Computer" with some crummy registry cleaners that just cause more issues, but this really ties into reporting problems ASAP.
How to files for users. For example we have a how to on how to use our remote desktop connection and VPN. They wont have to install it but they will have to use it so a brief written tutorial will save you tons of time repeating the same process to a hundred people.
Don't self diagnose, that's why you have an IT department. Even if you are handy with a computer at home, listen to a pro. You don't go to the doctor self diagnosed and demand medication do you?
*** happens, dont blame me or the computer, things break it takes time to repair learn to deal with it or you get a typewriter.
One for the IT people your job is to make everyone elses job easier. Don't make it harder or more complicated than it has to be.