I recently bought a Yubikey Neo which can act as a OpenPGP smart card. I'd like to use this to store my private GnuPG key. I've gone through the initial setup and I am able to use the smart card to sign and encrypt files. After the setup the smart card's key shows up in
gpg --list-secret-keys output.
If I lost the GPG keyring (say if my hard-drive died) or I want to use it on multiple machines, how do I get GPG to use the smart card?