Think of all the teachers/instructors you've had in your life, not just for pool but going back to elementary school through college and your professional life.
Some were OK, a few were great, a bunch were probably a waste of time. But often it was the individual that related real world experiences and lessons that made the instruction relevant to you.
It's the same for pool.
Over the years I've spoken to many guys about what pool lessons they've taken. I know guys who have taken lessons from some renowned players who said afterwards it was a waste of money. I know guys who have paid a lot for lessons from a professional instructor -- guys who run schools, have written books, and put out DVDs, and said it was a waste of money. And then there are guys who have had revelatory experiences with pros, as well as with guys who just billed themselves as instructors. And what it boils down to is that it's like anything else in life, whether choosing a doctor or a car mechanic: you do your due diligence and you take your chances and stay or move on.
It's going to be different for every player. Some guys, at their level of play, would benefit from a few words of advice from the guy playing on the table next to them. Others need help on technique from guys that study the biomechanics of the game. And others are more interested in advanced strategy.
Myself, I'd never take lessons from some guys because I know people who have and the reviews have not been good. Others I would not take lessons from include guys who teach an approach or have an emphasis on a particular technique that I don't agree with, or who focus on an aiming system that I do not believe works. Not interested.
But the guy who can relate real world experiences, share those, and relate it to my game... very interested. As an example, when I spent time with Dallas West, we reached a point in the lesson that went like this:
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And so it went, shot after shot until, without realizing it, I had run somewhere around 70-80 balls fresh out of the gate. When I finally missed (I had no shot and was frozen against the stack and missed a table length kick) he said, “You have a real nice touch, Lou. And, I know you didn’t want to get into basics, but… would you like to know what took me from being a 70-ball runner to the next level? Because I can see that’s where you’re at and it’s something you could work on.” And I said (wait for it), “Yes.” And he told me and frankly it’s not something I’m going to give away. You all need to see Dallas for that one, but believe me, it has been helping me *A Lot.* In this same vein, he showed me two shots and their variants that he said were essential for me to learn to excel at straight pool (I knew one of them from my 1pocket endeavors, but not the other.)
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IMO, you can only get that kind of stuff from an accomplished player who is speaking from first hand experience and is teaching you something from his life in competition and gifting it to you. That's the good stuff. YMMV.
Lou Figueroa