How do I study? It depends on the type of class I take. Lets say I'm taking a class that is based on memorization (reading) such as History or Biology. I'd take notes during lecture and at the same time write my own questions pertaining to the chapter/notes. After class I'd go home to read the chapter/notes that was presented for that particular lecture day, afterwards, I'd go to the questions that I've written and answer them based on what I've learned in a timely manner (time yourself, about 15-30 seconds for each short answer question written, because it's either you know it or you don't). If I fail those questions, I would make new ones up and go back to those old questions after I've read my notes over again.
If I was taking a Math class, I'd just do as many problems as I can in the book and/or study guide that the teacher has provided. If I'm weak on a particular area then I'd make up my own problems or go google some more to practice on. My goal is to solve as many problems as I can and at the same time be exposed to a variety of topics. Also, consider getting a small chalk board or white board to solve math problems on as well. It's what I use to study insanely and not to mention that it saves trees.
Classes are either memorization (history, biology, ochem) or problem solving (math, gen chemisry, physics). You get the drill.
This is how I study and so far I've maintained a B+ average for my first 2 years of undergrad as a six-year BA/MD student.
EDIT: Insane coursework during summer dragged my GPA way down below average. Nobody has time to take OCHEM1W/LAB, Cell Biology, and gain "Hospital Team Experience (a class that exposes you to patients in a hospital, my med school is connected to a hospital)," all in just 8 weeks.