Working and re-working problems is important for technical courses (e.g., math, economics). Be able to explain the steps of the problems and why they work.
In technical courses, it is usually more important to work problems than read the text (Newport, 2007). In class, write down in detail the practice problems demonstrated by the professor. Annotate each step and ask questions if you are confused. At the very least, record the question and the answer (even if you miss the steps).
When preparing for tests, put together a large list of problems from the course materials and lectures. Work the problems and explain the steps and why they work (Carrier, 2003).