DO keep the sky level between 30 and 100. Too high a sky level and the dynamic range is much reduced. Too low a level and the pixel rejection schemes get confused. DO adjust the high voltage before changing gain or offset. DON'T expect great guiding if you change the box size or location when guiding.
Large errors can result due to buffer changes.
DON'T turn the DTI box on. DON'T turn the PC off or disconect the cable from the PC parallel port while the telescope power is on. The pixel value as displayed on the TV is the digitized value, not display values. Guider Parameters Hit the 'p' key to verify or change the guider parameters. If you are guiding, guiding will stop.