Then type in dumpprivkey
If you type in help, it should give you a list of commands.
Once you get your private key write it down on a piece of paper, along with a public address for depositing anymore DGB.
You should also probably use a virtual machine to make the wallet so it doesn't end up being a copy of your wallet!
From then on if you ever want to get the money on that wallet back, go in the console and type in importprivkey (Your Private Key Here), and it will load that paper wallet into your virtual wallet. Make sure it's on a clean computer or VM though, because I believe loading a private key onto a wallet you all ready have funds on will just overwrite everything on there. Can't confirm though, never tried. It's also a pretty good practice to backup your wallet constantly, by going to (File->Backup Wallet) in case anything goes wrong.
You could always back up your wallet.dat onto a flash drive and store that somewhere it would be safe, but it just wouldn't feel the same as a paper wallet
Hoped all that helps.
EDIT: Just to clarify, any address under your "Receive coins" tab is what I mean by public address. It was probably obvious from the text, though.
Thx..Will try that on a live disto