How do you safely set up a offline deterministic wallet? There is a good tutorial for setting up a safe offline wallet with a regular bitcoin wallet here.

If I want to set up a safe deterministic offline wallet (i.e. Electrum). What would be the right steps?

Should I just store the seed, or also backup the private keys?
On a deterministic wallet the only thing you need to keep safe is your seed / passphrase to be able to restore it in the future

Here you can find a tutorial on how to make transactions with an offline Electrum wallet using your Master Public Key

http://electrum.org/tutorials.html#offline-mpk