Attending lectures is one thing. Paying attention during a lecture is another...but taking notes during a lecture is almost like an art. Essentially, note taking is a unique thing. Every one takes notes differently. Back at school, everything was spoon fed to me. What the teachers wrote on the board, I would copy it down. This method doesn't exactly work in university...unfortunately. When I got to university, I was pretty confused about how to take notes during lectures. Fortunately, my university uploads the lecture slides ahead of time, so I usually print them out and take them to lectures. What notes do I write down? Well it depends. It helps to read the lecture ahead of time so you can pay more attention to what the lecturer is talking about and you'll know when to add to the slides.
For me, I bring a laptop to lectures as I think it is easier to type my notes as I don't need to really pay attention to my typing and I can pay more attention to what the lecturer is saying. Plus, I type quickly so I can take down more notes. If I know I have a brief/not detailed lecture, I would tend to write down most of what the lecturer says. Some people find it difficult to follow lectures, so some people bring a dictaphone to record the lecture and to listen to it later when they have time and to take more notes. I think it's a good method ONLY if you go back and listen to the lecture. I'm a bit of a lazy bugger....so I know this method wouldn't work as I wouldn't go back and listen to a lecture and make notes.
Then again, some people don't take any notes and rely on their recommended/extra reading to get the notes. Also you need to know what kind of a learner you are. I'm not a great oral learner...I'm much more a visual learner so I need to see things written down. I can't remember things that are told to me. I have to either do it or write it down; therefore, note taking is a very unique thing and only you'll know what is best for your learning.
I wish I can tell you in more detail how to take notes, but this is something you have to try and discover yourself. Try different methods...and eventually you'll find what works best for you.