Go to
https://bitaddress.org, and save the page on your usb. You can check the sha1 sum if paranoid (search this forum for the bitaddress thread with announcements of the each new version with the sha1 sums).
Now disconnect a computer from the network, and boot it from a cd or usb with linux. Search the web if not sure how to do this, it is easy. Once in linux on this isolated machine, plug in the usb with saved bitaddress code, and open it in the browser. It will generate the wallet just like it does when you try online.
Ideally, you should now print wallet pages. If not, save the pdf on the usb, and shut down the computer.
Print the wallet saved on the usb. Keep in mind this may be the vulnerable stage - print it from an offline computer booted from the same live cd/usb, if possible. I print two copies that I keep in two different locations.
Format the usb (not the "quick format") or just destroy it.
You now have an extremely secure set of keypairs (your paper wallet). Treat them as such.
Alternatively, you can choose to trust Casascius, and just order his blank coins that you send your bitcoins to. He has gone through all of this and some more to ensure the security of his keypairs.
