And if you are looking for national/international advertising, KarateForums.com is a great place to advertise. Locally, I would say that local TV stations are a good arena if you can afford it. Radio and print ads like BD said are good. Also, if you want to take out an ad in the phonebook, so when someone goes to "Martial Arts" and sees the list of schools (if you are in an area with a few schools), your ad will stand out.