Dutchman,
A system's effectiveness is primarily dependant on your willingness to put in effort, not just in training, to learn why things work and to apply those principles throughout. I knew someone who actually learned a lot of good Kali from a horrible teacher, he was basically watching everything the instructor was doing and asked himself if it was practical, why or why not, and how to adapt things to make them better. This type of active learning will always make you better than someone who just wants to passively take in what the teacher says and become Neo. How many people out there have been training in some type of activity and make minimal progress over the years? Is it that they like "training" or they are training to improve?
The next step is to find a quality instructor, one who is on the same page as you. Hopefully he looks into the science behind movement and knows the principles behind something working as opposed to just trying to replicate movement and expecting the same result every time. It would be nice if the instructor has plenty of real world experience to back up what he is teaching, this is helpful in seperating a lot of fact from theory, but also it gives you insight as to their paradigms regarding training. Why is it that something works or does not work for him, or perhaps the questions should be why they are comfortable with something?
Another thing that makes a great instructor, and I know this sounds weird, is whether or not he will let you feel his body during a movement. Ultimately, the core of what we're after if effective and efficient movement, and a lot of times it appears as if very high level practicioners are barely doing anything and getting great results. Many people claim that the students are going with it and that it's BS, and in some cases they might be right, but what often happens is that there is a lot of movement that they just dont recognize. If you ever look at any footage of Mifune (
http://www.amazon.com/exec/obidos/A...61394/sr=11-1/ref=sr_11_1/104-8595616-8919910)
or of Okamoto (
http://www.daitoryu-roppokai.org/) they are prime examples of people who hardly appear to move.
I took a VERY hard shot this past weekend from a guest instructor who generated a lot of force with little movement, though he explained that his punch was actually generating energy from his calfs and feet, thighs, hips, shoulders, arms, and wrists, etc (entire body, basically). What seemed like a simple punch was actually 30 movements synergistically combined. It took a lot of training and thinking to become proficient at all of those movements and then to combine them but after years of training he can do it without giving it any thought. The scary thing is that he was actually going light on me