Make sure that you attend every class session. Classes held just before a test are crucial, for instructors will most generally hold a review. They will usually tailor the last couple of lectures to the content of the exam. Date your notes. Use a separate notebook for each class or get a notebook that has dividers in it.
Organization is the key to good note-taking.
If the instructor writes on the board, that's your cue to write it down also. If you don't end up with four, ask the speaker or another classmate for the details. Look over your notes immediately after class. Reorganize them or recopy them if necessary. Fill in any missing information or anything that might make the notes more clear to you.