Start every set by standing all the way up then lowering down into position! This lets your hips and low back lock into place for better execution. Keep a slight bend in your knees, knees rolled out and low back arched.
For beginners make them maintain scapular retraction the majority of the time. Once they get some experience and can let their scraps protract and retract efficiently during the row then you can have them do this most of the time. If they are having trouble keeping their low back flat have them look straight ahead.
Sets and reps can be whatever you need. You will have to use a little less weight with these than a dumbbell row on a bench, especially for beginners.
Not sure what it is about this exercise but it torches my back every time I do it. Try it out and hopefully you get the same thing. Or maybe I'm just a sissy?!?!