This.Try not to copy everything. You'll generally miss a lot of what is being said. Try to read the textbook before the lecture and only try to copy what is new.
Note how there's lots of people saying 'important = in book' - but what happens when the instructor strays from the book a little bit? How would you know if you didn't read before hand?
In general: math/physics lecture shouldn't really contain any suprises. Suprises are what you should write down. Being prepared for class will help you prioritize your note-taking.