Personally I never use digital mode, I go by combo of smart screen/audio tone and tone quality.. after a while the tone quality will be a dead giveaway to a good target.. by the way I would suggest going right into advanced mode.. even if you wish to use patterns.. when you get into advanced mode you can change the tone variabilty up to max, which helps differentiate good targets.. I use normal response to get the least fluctuating audio.. most good targets will give a solid single tone from all directions, where trash will most times read up and down warbly tones..
If you go into advanced mode and want to use disc, just hit the select screen, press clear and then scroll down the list to reject crown caps etc.. I would not reject screw caps or pulltabs if your hunting sites that might have indians, half dimes, 3 cent pieces etc.. listen for the quiet solid toned hits