Now, instead of just writing everything the professor says you can begin to listen for points of emphasis. If she spends 40 minutes talking about something, put a star beside it. You will see it again. Pay attention to the building blocks. If one fact builds on another or one math function leads to another, then that building block is likely a key point.
Old tests are also a great resource see what past professors have considered important.
Ask the professor for study questions. Most are very generous if you show interest in the material. Once you have a handle on what you think is important you can begin to consolidate information into meaningful categories. Once you have narrowed the information, look for ways to block it into workable sections optimally segments that could fit onto flash cards. If you can organize ideas or facts into meaningful categories it can be easier to recall.