David Bernstein has some excellent advice for second-year law students. In particular, as David notes, many students may not realize that most students work much less hard in their last two years, so if you work as hard as you probably worked in your first year, you have a good chance of getting better grades.
Let me offer some additional suggestions:
1. Seminars. Take seminars--and if your school has them, graded faculty workshop courses. They generally offer interesting reading, writing training, the opportunity to get to know professors better, and high grades. [I am here assuming that the curve is substantially higher than in lecture courses, as has been generally true at the six law schools at which I've taught].
2. Independent Study. If your school has possibilities for independent study with a professor, do this both years (with two different professors). The advantages are the same as for seminars--only these benefits are usually realized to an even greater extent. Also, you might get a publication out of it. In choosing whom to work with, try to choose a professor who has successfully supervised or collaborated with students on publications before (ask other professors for this information). For example, on the Northwestern faculty perhaps a third to a half of the prominently published student work has come from working with just a few professors; the most outstanding supervisors on this score have been Steve Calabresi, Ron Allen, Marty Redish, and (before he left for Columbia) Tom Merrill. If no professor has successfully supervised students on independent study, at least pick a professor who publishes a lot, because he or she usually has ideas to share.
3. Law Review Fall Write-on (but only at schools where it often works). A few schools (probably less than 15%) have true open-access law review possibilities in the fall of second year, where at least a quarter of the second-year staff of the main law review are chosen by writing a near-publishable draft of a student note during the semester. Most schools have a write-on option for publishable work, but they are not really geared to accept people through that route, so almost no one succeeds at it. If it is not common at your school to write-on by this method in the fall, I would usually recommend not trying, because it is much too easy to get discouraged. But if access to the law review is truly open and substantial numbers of fall write-ons are selected for the review each year, then I would recommend trying. Work closely with a professor to refine your idea so that you don't spin your wheels, and then kill yourself for the three months it takes to write on. Follow the advice in Eugene Volokh's book and make sure that your blue-booking is exemplary. If doing cite-checking of law review manuscripts is allowed for those merely writing on, volunteer for at least some of this work and make certain that you ace that assignment. For those trying to make the main law review (or for those on the review trying to make the managing board), making an extreme effort for just a few months in the fall term of second year can pay big dividends in the long run. As for working on other than the main law review at your school, I'm not sure that I agree with David. He may be right, or he may not be. Certainly, if you strongly desire that experience, I would do it. As to whether it matters on a resume, I've always thought that being an editor on a less prestigious law review was a plus, but he might be right that it may not be worth the considerable effort, both in making the managing board and doing the editing if you make it.
4. Different Sorts of Educational Experiences. I would generally recommend doing some different sorts of educational experiences because the learning curve is especially steep at the beginning of a new experience. If you don't do law review, you might consider working in the clinic or doing an internship off campus. Both can be terrific for learning how to practice law. While I think that doing moot court can be educationally sound, unfortunately I don't think that it helps your resume unless you win at least some level of the competition. At schools that give a lot of course credit for moot court, that might offset the time spent away from other work, but otherwise I would be cautious about participating in moot court--unless you just love that sort of thing or you realistically have a good chance of winning.