I don't attend any lectures at all and usually get straight A's without much work, in many subjects (at least in the types where you simply memorize text and use the theoretical framework on a case on the exam) I've gotten A's with 1 or 2 days of work in total per subject, per semester (usually before the exams) on several occations. (And I'm not writing this to sound like an arrogant prick, it's simply a fact that proves these concepts work) -> Luckily, many of the teachers in my university don't require you to hand in assignments during the semester ;D
My point of view is that it's about 3 things:
1: The ability to memorize all relevant information in the subject in a clear and organized matter (meaning that you don't just know a lot of randomly selected "facts" from the textbooks (something normal reading or attending lectures tends to produce),
but that you know the entire core curriculum in a systematized way so that you know all the concepts/scientific terms and so on and all the interrelationships between all the key stuff)
Later addition to this post: When you go through process 1, make sure you comprehend W H Y things are the way they are. That means that AFTER you're done with stage 1, spend some time simply going through the things you've memorized, see how different areas connect, figure out what kind of key logic that lies below the "surface" (for example, deconstruct proofs and see what kind of logic is used to make them: "Why is it like this?" "Could I come to this conclusion by inventing my own method?" "Do I really understand every concept used here?" "Have I seen a similar train of thought in another theory/Proof/whatever ?"). When you have done this enough, you'll more easily grasp the key ideas behind different academic material because you have become familiarized with the underlying logic that is found again and again in many different areas..) Just like Richard Feynman said: Learn to understand, (and memorization is the first step), and make sure your knowledge is not fragile (many "difficult" assignments are difficult because it's always not clear what kind of theory or whatnot to use to solve it).
-> Again, if you memorize precisely and smart, most of these things fall into place quite fast if you spend some time reflecting over the material afterwards. Also, understanding comes easier the more you actively try to achieve it.
2: That you know how to solve problems, have some kind of problem solving algorithm that you have experience with
3: Know how to structure your exams and write it in a systematic manner.
I think step 1 is the most important step of them all. I see many students attend every lecture in many subjects the entire semester, but when you ask them for something simple like "what's the 3 parts you can deconstruct scientific validity into?", they have no clue even though it's been repeated many times in the lectures. Many people will argue that "it's the understanding that's the important point, not the memorization", but if you think about it, really comprehending something and using it optimally is not possible without memorization of all the sub parts. A house is not standing solid without all the parts installed.
So, in mathematics and physics, memorizing everything before you do a single assignment is usually a smart thing, because most of them is a piece of cake once you have all the formulas and techniques in your brain.
Even easier is business courses like organizational theory and such. If you have all the different theories in your mind at the exam, you can go: "In this case I will discuss the relevant (that you define) problems with theory A, Theory B, yada yada yada" and so on, then present my own view/creative ideas in this matter before coming to a conclusion. It's pretty hard for a teacher NOT to reward a student that has discussed a given assignment with all the theory needed, shown his/hers capability to offer his/hers own views on the subject, before coming to a solid conclusion with a straight A.
Each subject has a theoretical framework that is presented in a clear and systematic manner in the textbook and/or lecture notes (that most teachers upload online).
The real trick here is to use effective memorization techniques, mainly turning the key concepts of the subject into pictures, and then make mindmaps of each area. What I do is to simply memorize the mindmaps as pictures (via mnemonics) so that I know the core theoretical stuff word for word and all the interrelationships, and then spend some time practicing retelling the information to myself out loud or to others.
Works like a charm.
I've found that I can pretty much memorize the key concepts from 1 month of lectures in a few hours (it took much longer before I got this stuff down) and it also pays to memorize some "aux" information to "impress" at the exams.
Besides that, knowing how to structure the writing on an exam is always a good thing (as already stated), and this stuff is easy to locate on the net or in books.
When it comes to more math/physics type of subjects, effective memorization is extremely useful, and having some problem solving experience is also a huge plus.
Good luck
