Boxed so that nothing can be bent, plus wrapped securely (preferably in some bubblewrap) and with the actual album in a sleeve but outside of the cover - if there's any chance the record could shift around inside the cover, the sharp edges can actually damage and tear the cover (I've sadly received a couple of limited edition albums where this has occurred).

You can get boxes sized especially for LPs, but pizza boxes (not used ones 🙂 ) are also a common way to send them, which you can also buy online in small or large lots.