Topics are the most straightforward thing you could take note off. You could literally just write the title of the material or subtopic you are being taught in class. However, doing this mindlessly could present problems when doing further revisions.
When listening to lectures or taking down notes, its important to write a guideline at the top of your notes. The difficulty of writing this guideline can range fro simple to moderately simple as all it is is a list of the topics and subtopics within the module or lesson. This will allow you to see the bigger picture when studying and refer to a specific section when you need to.