Another fertile source of Note topics is your summer job. If you see anything interesting at your summer job, talk to your colleagues and supervisors about whether they think it might make an interesting Note topic. In addition, most practicing lawyers generally have a few issues in their heads that they wish somebody would research and write on. Some students work with professors on generating Note topics and writing their Notes, either through seminars, directed research, or on an informal basis. Each has unique advantages.
Seminars can be a great environment in which to both find a topic and write a Note.
If you are interested in the area of law covered by the seminar, you will be learning about that area as you write your Note. If you are interested in being in a seminar, you should rank it first or second on your course preference listing, as they fill up quickly. This sort of approach works best when your interests align closely with those of the professor. Professors are generally happy to help, although they may be less willing to devote time to your project in an informal setting. There are, of course, other ways of generating Note topics and of writing Notes.