Later you may have seen that participating in Apple’s OS X Beta Program brings you all the beta releases in your System Updates, even after the official release, which you may not want at this time.
If your Yosemite is in english language you can find the option to disable beta updates in System Preferences > App Store as in Kirk McElhearn article… if you’re lucky enough to have a more verbose language (e.g. italian or spanish) there’s a gift: Apple hadn’t enough space to insert the button label, so you have no easy way to disable beta updates!
Once you come back from tweeting that Cupertino #epicfail, in the comments of the mentioned article noar tells us the solution: the option is in CatalogURL value in /Library/Preferences/com.apple.SoftwareUpdate.plist file, so fire up your terminal and issue:
$ sudo defaults delete /Library/Preferences/com.apple.SoftwareUpdate CatalogURL
If you want to subscribe back the beta updates, you only have to launch:
$ sudo defaults write /Library/Preferences/com.apple.SoftwareUpdate CatalogURL "https://swscan.apple.com/content/catalogs/others/index-10.10seed-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz"
You can, of course, switch the language back to english, disable the updates from System Settings and switch back to your language, but the command line is way more fast.