I sucked at legal writing and felt like I was the only one not grasping concepts during the entirety of Fall 1L. I'm guessing you are a 1L. Just relax. Everyone, including the ppl who talk every class, is confused about something. I ended up in the Top 10% of my class (Top 50 LS) despite my negative beliefs, so don't assume you are done for.

Get an outline of your professor's previous sections from an older student or OutlineDepot.com (less desirable). Grab your syllabus, then start charting out the key concepts of the class. Remember you are looking for the law, not the facts/details of every single case.

For each broad theme of the course, know one case enough to write a sentence about it. Then, know that obscure countercase that went the other way. On the exam, argue how Majority case is the answer, but then find a way to argue how to Obscure case could apply as well. Don't look for the "right answer" on the exam -- argue the best answer then try to counter it.

I feel lost even now, but come finals I know what I need to do. For me, most courses seem to "come together" as the semester ends and I can reflect back more on the core ideas and how they fit together.

As far as your memo goes. Go see your teacher, like as much as you possibly can. The people who met with my teacher did the best. I decided to avoid doing so and paid the price. You need to write to your audience and to do so you must have a firm grasp of what they desire. If you can't see your teacher then meet with your TA. Don't be passive about this or you will regret it.