In order to learn martial arts training, you must take the proper classes and be professionally trained.
No matter what anyone (salesmen, business or otherwise) tells you, you cannot learn martial arts training on your own. Sure, you may be able to learn a few moves from a book or an instructional DVD, but you will never be a good fighter or be able to successfully defend yourself in a real life situation without hands on professional training.
When you are in the process of choosing the right class for you, do not just look at the school. You want to make sure that the instructors are professional, knowledge and dedicated to what they do. If the instructor is lax it does not matter how good the school is. The ones teaching you are much more important than the walls in which you are being taught, so take your time choosing and get all the information you can about the instructor before settling on one.