The problem with cramming for science classes is that you actually need to retain the stuff for later. [...] The part that I bolded is your real problem. You need to address this right away.
I agree, chafdorn. Try to learn the concept and fit what you're learning into the "big picture" while you're in class. (As a bonus, if you ask questions directed to the overall concept rather than necessarily to the specific example, your instructor will probably be impressed.
😉) Use the questions in the book to understand the nitty gritty.
My opinion - although I'm sure I'm going to have to memorize a LOT of stuff for Pharm school - is that it's fairly pointless to memorize great lists of facts, especially if you don't understand the underlying concept. In the "real world," you'll be looking these lists up in books / on the Internet (and in the academic world, you'll be loading these into your short term memory). Don't get me wrong - there are things you Absolutely Have to memorize, but these charts and tables are few and far between. If you have a head for memorization and a good memory, it really does help to memorize all of them, but for the rest of us, it's not realistic.
To the OP, I think you're starting to go through a change that most people experience upon hitting college. The timeframe changes based on personal ability and other situational modifiers (such as the classes you take, etc).
The change is from a high school student - who only does homework because it's required for the grade, attends class because otherwise your parents will get a call from the truancy officer or "The Office," and doesn't think of school as "cumulative" since each course doesn't really build on the last so as not to leave anyone behind - to a college student. A college student has different motivations - learning it for the future and building on past experience, thinking of the instructor more as a guide and leader than the "end-all-be-all," taking responsibility for your own education, and being in class because you know it's a good use of time rather than because you have to be.
The higher your natural ability, the longer you can skate through college using the same tactics and attitude as high school. You'll find you understand the game better and college is more rewarding, though, because your outlook on it has changed.
P.S.:
My usual pattern was to go way overboard studying for the first test of the semester so I knew I got off to a good start and adjust as needed from there to maintain the high grade.
I use this tactic for several reasons. First, I have no idea what the test is going to look like, and how harsh the instructor is going to be grading. Look at the first test as a way to learn how the instructor wants to teach and adjust your studying / note taking accordingly. Secondly, I'm fresh and not yet burned out.
😛