You will have difficulty reading many discs if you are using system 6 (I recommend upgrading to 6.0.8 in any case). You will need to find the desktop manager init and place it in your system 6 folder. This will avoid your getting stuck in a loop in which the OS attempts to rebuild the desktop of the CD.

Beyond that, you will need to observe the usual Rules of SCSI, amended for the Compacts: Have the external drive supply termination power; make sure that a terminator is present; make sure that each device on the bus has a unique ID; sacrifice a chicken.