The first thing I do when I have a new class of university students is separate them into fruits and vegetables. This is because when you stand up at the podium and look out at a hundred students with black hair and black eyes, it's like addressing a crowd of straight pins with black heads. It's practically impossible to remember all my students' names unless I divide them into fruits and vegetables.
In secondary public schools in Japan, the students have to wear name tags. In addition, I've seen some high-schools give teachers large photos containing head shots of all the students in each class. This photo corresponds to a seating chart, so that teachers can identify students according to where they are sitting. But no one wears name tags in university classes, where the classes are often much larger. I've heard of university teachers who take Polaroid photos of each student so they can learn their names.
But the fruit and vegetable technique is much simpler. You don't need photos or seating charts. It's so easy, anyone call learn all their students' names within a week or two. It just requires a shift in, uh, perspective.