I went to a seminar that was advertised on a TV ad. The ad said, "Free seminar will teach you how to become financially independent through tax lein certificates." I went to the seminar, and all it was was a sales pitch for the "Tax Lien Certificate Course." They didn't teach me anything. The guy seated next to me bought the "course." He let me look through it, and it was a notebook, a bunch of paperback magazine type books and a few glossy pictures of people giving testimonials standing by luxury cars. Funny, the testimonials only included the first letter of their last name. There was also a fancy platic folder that held 6 cassette tapes. The whole package probably costed about $10 to make. I didn't see any "secret contacts" or "secret techniques."
Usually, probably always, these companies make money from selling their get rich course, not doing the scheme from the course. I've done a few tax liens myself, and the best way to learn is to talk with people who have done them, such as the people on this board, and check with your local courthouse. They might even have all of the information you want for free online.