If all I have to do is filter through spam mails (I only got 1 out of 50 odd so far) and reply to people who just want to know how much you charge and that is it, it is not much of my time wasted. The initial reply to the emails is usually a copy/paste task. If someone said to you, all you must do is go through 100 emails, and if you do this you will have 10 new weekly students, that is a pretty good deal if you ask me.
I don't think we want to try to find out a single way which works best to recruit students. It is always good to advertise in as many ways as possible to get yourself heard out there (that is if you are looking to expand your student base more so than what you already are doing).
Now 3 weeks have past and I have 4 new students, 2 more that want to meet up for interviews, plus the manager of a private music school is meeting with me next week wanting to talk with me about teaching at their school for 1 day a week next term. Pretty good stuff for sitting on my ass.