Auto-Save and Versions are excellent features in Mac OS X, but some advanced users are annoyed by  them as they often don’t want to save intermediate versions of their work.
Moreover some apps write lots of data on disk (e.g. iMovie and iBooks Author) and this can shorten the life of SSD (look here for more tuning for SSDs).
If you know the name of the app plist you want to disable auto-save and Versions for, you can just plug the name into the defaults write command:

If you don’t know it then you can find it with the following command:

Now if you enter the Versions window, auto-save list will be empty and there are no versions to restore to. You’ll probably want turn off File Locking too.

NOTE: some sandboxed apps require another command in addition:

This is expecially true for TextEdit as it is the only Apple app that uses “old-style” autosaving and this causes issues with the sandbox in Lion/Mountain Lion.

NOTE2: It seems that the preference can be set globally but it may cause the login process to become very slow and possibly cause other unexpected behaviour: