Hi there.
So know that I started to life in the more recent Mac World (through an donated G4, thanks a lot! ^.^), I also feel the need to get a bit more to grips with this little fella.
The most basic stuff I did need in recent time:
Eject CD / DVD if "stuck":
1. Through Open Firmware
Press ALT + Apple + O + F after the beep as you turned the Mac on.
A white command line will apear. Enter eject cd and press enter.
You can do this again to close the drive.
( And mac-boot if you want to boot or shutdown )
2. Through Comamnd Line \ Terminal
drutil list shows the installed CD Drives.
drutil eject NUMBER does eject the CD from the numbered drive.
Target Disk Mode \ Firewire:
If you got two Macs, the most impressive thing is the Target Mode.
In Target Mode, you connect two Macs via Firewire Cable, start your Target Mac and press T as long as some nice Firewire Logo appears, and start the second One, with, for example, ALT Key pressed. This will give you an possibility to choose your Bootvolume. So, as Target Mode is active and the Macs are connected, also the DVD Drive and Harddisk from the Target Mac does show up! You can even boot his Mac OS! Cool. Ain't it? Thats useful in cases of Harddrive Crash or for example, If you want to use the other Macs DVD Drive if your other Macs is dead or not existing (Mac Book Air?).
Also you could set the "to be installed" Mac in Target Mode, boot into Mac OS install and install on the Target Macs Harddrive. So, you got some options, use them! ^^
Ah.. by the way, as this site figures out ( http://lowendmac.com/osx/leopard/unsupported.html ) you can also install Mac OS X 10.5.1 Leopard on an old 400 MhZ G4 by starting it in Target Mode and install Mac OS X onto its Harddrive! Cool!