Mermaid:
I don't have any college kids, so I have no experience to share as a mom of college kids (will be someday, though, and I'll remember this thread and turn to you for advice if I need it!). However, I teach MBAs and my research is on "what predicts success" in life and work. I leave the definition of success to the individual (whether it's climbing the ladder or having lots of time to be at the beach or both) since success means different things for different people. The only thing I would add to a general definition of success is that one should be making some kind of contribution to the world as well -- it can't be only self-focused.
Also, though my kids aren't in college, I went to college and must admit I wasn't a stellar student. I didn't complete my undergrad degree until I was 28. But I did find a topic I loved at age 26 and decided then and there that that was what I would want to do for the rest of my life and that I would go to grad school. So, have heart. Some of us are slow starters and our brains don't kick into full gear until we find what we truly enjoy -- what really engages us. And we end up the lucky ones because we spend our lives doing what we truly enjoy rather than for the grades. So, your son would want to be noticing what really engages him at college. Also, I think that for people who can disengage from classwork that it's harder to do good work if the teaching isn't very good -- and sometimes that's the case.
That said, I believe college students have the responsibility to do their best work. So, I agree with the other advice people have said on this thread -- he needs to pay attention to his study habits, pay attention in class (I had a hard time with that one if the course was dull to me -- and in fact it really may have been dull), hand in assignments on time (that were done to the best of his ability), connect with students who do good work and ask them what their habits are, be respectful to faculty and find something to be engaged in in class. I also recommend to students who are struggling that they identify the best teachers (sometimes ratings are posted somewhere) -- people who love what they do and who enjoy students -- and take courses from them if possible.
As for what predicts success (I'm sure I like studying this because I was such a slow starter!), this is what I've learned from research so far:
IQ predicts at most about 25% of success. Assuming someone is in the normal range of intelligence somewhere, IQ predicts about 9% on average. (this isn't my research - it's the research of Robert Sternberg and it is debatable of course).
The characteristics that predict success (less debatable) are:
Conscientiousness: Hard work, dependable, organized, planful
Proactivity: Wanting to fix things that are a problem (So if your son turns around and does better work next semester, he may well be proactive. Students who easily get good grades with little effort may not develop the skills at proactivity. So this experience could turn out to be a very good one for your son if he turns his grades around. He'll know how to "fix" problems rather than "quit" when the going gets tough.)
Believing in fluid rather than fixed intelligence: Believing that intelligence is influenced by the environment one is in. People who believe in fixed intelligence tend to quit too easily when they hit a bump in the road. People who believe intelligence is fluid tend to figure out how to do better next time when they hit a bump. (So your son wants to find environments in which he can do his best or adapt environments so that he can do his best -- e.g., adjust study habits, hang out with people who bring out the best in him, identify good professors, etc.)
Learning orientation: Approaching projects with the intent to learn, not to show that you're better than someone else or to avoid failure (both result in taking on projects that are too easy for you). (So your son wants to see the first semester as a learning experience and figure out what he learned from it that will help him do better next time.)
Creativity
Practical intelligence: Figuring out how to use what you know in a practical way that matters to others
Emotional intelligence: This refers to emotional stability (appropriate emotional reactions to the situation), self-awareness, and social skills
Positive emotions: Hope, resilience, optimism, forgiveness, gratitude (gratitude is a big one in terms of having a good life -- if you're not grateful to others and for what you have, it's hard to feel successful -- and that feeling of gratitude comes from within, not from the external environment). (In your son's case, it sounds like resilience will be important and turning the situation into something that is positive in the long-term -- "I really got a chance to see what happens when I don't try hard enough" or "I really learned I need to develp good study habits.")
I'm sure this is too much information, but I hope some of it is helpful. Frankly, I'll take a student who has learned some hard lessons than a student who gets easy "A"s anytime as a student or future employee anyday. They probably learned more life lessons from their experience and have some very interesting stories to tell!