*whew* Wow, first semester is down. I feel accomplished. So, having survived it, here are my tips for anyone that is new and just starting the evening MBA program...
1) This is not an undergraduate degree. What I mean by this is that while you probably will expect to go off of your undergrad experience (I know I did, it was all I had to judge by), it will NOT be the same. Professors are different, grades are different, expectations are different. It's just... different.
2) Grading is based more on how the entire class is doing than on a specific scale. From what I can tell so far, most teachers will give you a loose grading scale. The scale seems like it is probably approximated based on how previous classes have probably done. But grading is more based on a curve than anything else. You can do horrible on a test, and if the entire class did horrible - well, it won't be as bad as you think. The professors are only permitted to give out A's to a certain percentage of the class, so the A's will go to those that are the best of the best - not all of those that get a certain grade. This is all from what I can tell of my experience of my first semester, of course. The jist of all of this is that if you think you are doing badly in a class - you are probably not doing quite as bad as you might think.
3) The little things determine the big things. Remember as part of your undergrad how you usually had some form of homework to do and turn in at least every other class period? Not so here. Most classes will have around four or so things that your entire grade is based on. Some classes have a participation, some don't. All have homework/reading for pretty much every class, but it is usually not turned in. Instead, the homework builds on the bigger things, the things that your grade is based on, such as projects and tests. Find out what these bigger assignments are early, and stay prepared for them by doing as much of the homework as you can, even if it doesn't have to be turned in. It's difficult to stay on top of all of it, but make sure you can at least follow the discussions in class.
4) The rest of the class very likely feels the same way as you do. I mean this in a way as feeling overwhelmed and like you are not doing as well as you think you should be. I'm very hard on myself, and I got pretty good grades in my undergraduate career, so in the back of my mind, I expected the MBA program to go just as smoothly. And well, I felt kind of like I crashed and burned early on. But the outcome was better in the end. And from talking to fellow students, almost all of them had similar experiences and concerns.
5) Hang in there. It's expected that you go in not knowing what to expect. How could you? This is your first MBA program (I'm guessing) and probably even your first masters degree. So just pay attention, go with the flow, learn from each test/assignment what is expected of you, and go into the next test or project prepared. You will survive, and it will be a learning experience that will help you through the rest of your MBA career.