Waiting until the last minute to start a paper or a project might have worked for you as an undergraduate, but you won't get away with this in an MBA class. If you have a paper due in a week, work on it a little bit each day, or schedule some time a few days before it's due to complete it. If you are going to school part time while working, do homework on your lunch hour, or get up an hour earlier and get some done before work. However you do it, finding a way that works for you to make homework a part of your normal life will help you to better manage your time.
Learn to make schoolwork a priority. This means that sometimes you may need to stay in and study on a Friday or Saturday evening, instead of hanging out with friends, taking a trip to the mall or watching the big game. Just remember that this is only temporary, since you will only be in MBA school for a couple of years. Also, don't be afraid to ask your friends and family for help running errands or getting chores done around the house if you're feeling overwhelmed.
Put your best effort into successfully completing your classes. When you have to write a paper, do a thorough job on the research and proofread it. Do the assigned readings before class so you know what your teachers are talking about during lectures and can participate in class discussions. MBA classes have a ton of group work, so do your best to be a great group member, by doing your fair share of the work, responding to emails and being willing to listen to other group members' points of view.
Even though you want to put your best foot forward in your MBA classes, make sure to find a way to balance schoolwork with the rest of your life. Don't get so consumed by your studies that you forget to pay bills on time, lose track of friends, stop doing laundry, running errands or spending time with family. As long as you manage your time wisely, you should be able to handle it all, just maybe not all of it at once.