Most forgetting occurs within 24 hours and you can slow the forgetting curve dramatically by reviewing within this period. This can be very useful at test time, since the amount of material you need to relearn will be much smaller. It is wise to take down as much material as possible during each lecture. I will let you know if you do not need to take notes. They are extremely important, and you will probably not remember them if you do not take them down.
Some students begin each class taking lots of notes, then get tired and quit.
This is unwise, since the material at the end of the class may be the most important part. By the same token, do not begin a particular topic by taking lots of notes, and then slack off. Such transitions will almost always be indicated. Your course outline should have these identified. When the board material is in diagram form, the diagram should be copied exactly, not summarized in words only.