How can I encourage good note-taking? Often, college students do not always know what kinds of notes they should be taking.

How can I encourage students to take notes more efficiently and more effectively?

In one of my lecture-style courses, I have lots of organized information on my lecture slides for reference purposes. This allows me to introduce more material and work through more examples than I would otherwise be able to do. The lecture slides use signposting in order to give structure and to help students organize their notes logically. I post the slides to our course web page before class so students can use them in class to aid their note-taking. I have discussed with my students that I do not intend for them to copy my slides into their notes and that the slides are meant to used as reference. I've mentioned that I want them to be more strategic with their note-taking: they should be taking notes on major themes, key ideas, and processes, as well as on things that we discuss that are not in the slides. This works for some students, but I want to do better for all. The current semester is almost over, and I'd like to specifically address this for next semester.

Note that I am not asking how to take better notes, as others have asked here (example), but rather how I as the instructor can address this in the classroom to improve students' note-taking skills.
This answer assumes that the course you are teaching is not about note-taking itself.

Make sure there really is a problem to address

Are the students who you think take bad notes also performing badly in the course? Different students have different ways of taking notes, or even different purposes (for example, I used to write down as much as I could because that would help me learn the content afterwards through "muscle memory").

There is not an unique "correct" way of taking notes. If you know exactly what notes the students are supposed to take, then probably they do not know, so why not provide those notes to them? That would help them much more, and the goal of your course is to transfer knowledge about a specific topic.

If, after considering this, you still want to get the students to learn these note-taking skills, you will probably have to dedicate some lecture time to explain how they should be taking notes. Having them submit some of their notes as an assignment will also help. After all, if it is not part of the course, many students will not be motivated to do it. Keep in mind that students have developed their own learning methods for many years, and changing to a new note-taking method might actually make some students perform worse while they get used to it.