My brother is graduation from UM Law in a month or so. He never got less than an A in his undergraduate program. Law School is much more challenging and time consuming. You will have to spend more of your time studying than in undergrad if you want to do well since you are pretty much competing for grades with the other students. I might be going to law school as well.
The best advice i can give you based on what he has told me is:
Get rid of everything that does not need to be in your life. That includes drugs, drinking, stress, time consuming hobbies. Friends are very important but you really have to cut them off or they will drag you down. Spend all of your time studying. You almost have to isolate yourself. Absolutely no drama, get rid of it all. If they are true friends, they will understand.
You will read more than you could ever imagine in law school. If you aren't spending at least 50 hours per week outside of class reading, preparing, studying, its not enough. I don't know your financial situation but even if you have to drive a crap beater car for the next 3 years, its better than having financial obligations that stress you out. Don't break any laws, don't ruin your credit, don't give any legal advice. Every time you do something, ask yourself if it could jeopardize your chances of getting your license.