When I started here I never realized how much more rigorous the courses would be. I was kind of put in the deep end with the hardest course that I have taken this year being CMSC216. It is a lecture class with hundreds of people and not enough professors/TAs to go around, so it was up to the students to help each other learn. I realized that discussion was the only reasonably sized class I would be in, so that is the time to ask questions and stuff like that. Also, if you are having homework trouble, go to the TA office hours as they will sometimes just give you the answers if they are nice. I also think that the math classes here were 10x better than AP courses in high school especially for stat classes. I also came from a high school without a big emphasis on finals, so finals week was an adjustment for me.
Talking to professors is not that hard though, you just have to go to office hours and email them. This is what I did for 216 and it ended up helping a lot for my projects. If you get to know the right professors, you can email them about research or internship opportunities. Even if they do not think you are the right fit, they can lead you to others who can help you out.
Adjusting was really hard the first semester because of my high workload but my second semester was a lot easier and gave me room to relax. I would say that study groups are kind of important for harder STEM-based classes, but you should always have at least one person to check your work with if it is allowed. Plus you can make friends out of them so it's a win-win.
I don’t think I was really unprepared for anything academic, but I think that it is really easy to fall into a loop of not going to class because most lectures are recorded, but this is not a good idea. Even the recorded lectures are sometimes blurry or don't show some parts of what the professor is writing, and some are not recorded at all (or they forget to record it). But I will say that the discussions for some classes (CMSC250 for me) were a complete waste of time while some were absolutely required to pass the class (CMSC216, and in STAT400 they give you the homework answers in discussion). If they're mandatory, then go but otherwise it usually does not hurt to not go.
Scheduling in these past 2 semesters has been awful. For the first semester I was in LTSC and could not schedule CMSC216 until classes started, causing me to get an 8am. I became a CS major in the winter but the same thing happened next semester and I could not schedule CMSC250 until classes started. I am currently dealing with another scheduling conflict for the fall, but I think I got unlucky this time. Just schedule your courses ASAP to prevent future headaches.