`ZZ` is great when you want to save. If you're looking at a read-only file, or just want to quit a file without unsaved changes, I personally prefer `Ctrl-w q`. I do a lot of windowing in Vim (controlled with `Ctrl-w`), and if you follow that with `q` (and you're on the last window of the session), it will quit Vim. I have Ctrl mapped to Caps Lock, so I can do this quite quickly.