Terminate the last internal unit on the SCSI cable, terminate the last external unit on the SCSI chain, do not terminate any of the other units.
Yes, all good general advice, there is some Amiga hardware that strays from this as in my GVP '030@50 in my A2000. This unit has no termination. The answer I got at the time was that the scsi cable is so short, it worked better without termination? :-?