From a security standpoint, I would not use an admin account for your day-to-day stuff. Make it a standard account. And if you use Safari, go into Safari preferences and uncheck "Open "safe" files after downloading."
I also don't let Software Update automatically update the OS. I download the updates manually when they come out and wait about a week to see if the update is causing widespread problems. Although rare, there have been some FUBAR'ed updates from Apple. Let others doing the testing for you.
Another way to deal with updates is to keep a cloned partition of their boot drive handy for back up purposes (I do this at work). Before you run software update, just make sure the cloned partition is current. If you have any problems, you can just go back to the clone. Super Duper or Carbon Copy Cloner work fine for this purpose.
Of course all of these things are overkill and probably not necessary. 99% of users will likely never have a problem that these steps would prevent. I tend to be cautious though.
-KeithP