Your son seems like he is prepared to change some things to do better academically, so he is already one step ahead of many other underachievers.
Here is my Rule#1 advice to my advises looking for help. Stay away from the residence hall!!!! What I really mean is get on campus by 10am at the latest and do not return to the RH until 6pm dinner time. Use that core time attending classes, doing assignments, studying, and review.
Rule#2 Take good notes using the Cornell method.
The Learning Toolbox - Cornell Notes Cornell Notetaking Method Custom PDF Generator
Rule#3 Find a comfortable place to study with minimal distractions. It may be a library, empty classroom, student union room, gallery space, etc. And take frequent short breaks(5 min/half hour).
Rule#4 Form/join study groups but maintain academic honesty w/re to graded work.
Rule#5 Make a schedule for long assignments and stick to it.
Rule6# Studying for exams is best done in short review over the course of a week rather than a last minute cram session.
Rule#7 Take full advantage of university programs such as tutoring, writing labs, test review sessions, and instructor office hours(which can be less intimidating if done by members of the study group).