First of all, you have to flash the chip first, it doesn't come pre-flashed with bios. I have never done this, so if you don't know how, I can't help with that.
If you had a dreamcast and made backups of the games, then you will be somewhat familiar with what you have to do. (Except xbox is nowhere near as complicated)
After you modded the xbox, you have to set up an "evolutionX" dashboard onto it. This replaces what the xbox boots to, also allowing you to FTP to the xbox through a network using a program called FlashFXP (or other ftp programs).
Dashboard tutorial: http://www.xbox-scene.com/articles/evox-install.php
After you set up the dashboard, open the tray of your xbox to turn it on, then after the xbox loads up, put a game in the tray and close it. Connect to your xbox with flashFXP and browse the "D" drive. This is the dvd-rom. All you do is ftp the files on the xbox into a folder on your PC.
Copying tutorial: http://www.xbox-scene.com/articles/evoguide3.php
Then, use a program called "Xiso" to make an xbox iso image. If you burn the files strait to the dvd, they won't work. Just burn the iso image with either Nero, or PrimoDVD.
Oh, and any dvd media should work, as long as the game fits on the disk. And for evolutionX, burn it to a cd-rw so you don't waste a dvd (and it might be updated)