If one is serious about improving their OTB skills, how important is a chess coach? What can a coach do for a motivated player that books and online resources cannot? How does one go about locating a coach that will maximize a players potential?
A good coach can help a motivated player improve faster by guiding him or her
to better training resources and by providing individualized instruction.
If a motivated player's happy about one's rate of improvement without a coach
(and wants to save money), then that player need not hire a coach yet.
But many, if not most, players reach a stage where they keep training hard without
improving, if at all, nearly as much as they hope. Then a coach may help.
I knew a longtime player who was highly motivated and had peaked at USCF class B (1600-1799)
without improving for many years. He told me that he owned several hundred chess books.
(He also told me that he found it too hard to understand many of these books on his own.)
We played a training game. He (as White) was booked up and obtained a slight
advantage out of the opening. Once he had to think for himself, however, he
was gradually outplayed and could not hold an inferior endgame. After I
explained various subtle inaccuracies that he had made, he remarked that he
had learned more from me than after trying to read many of his books.
As an analogy, some people (including myself) are able to read a mathematical
textbook and teach themselves without much, if any, need for a human teacher.
But most people learn better when a human teacher can offer explanations and
point out their individual errors.
I would add that a coach who's good for some players may not be as good for others.
GM Mark Dvoretsky was known as one of the best (and most demanding) coaches in the world.
IM Josh Waitzkin (the hero of the film 'Searching for Bobby Fischer' ) was very
unhappy with Dvoretsky's teaching style and said that he did not learn much.
Instead, Waitzkin preferred a less famous trainer. Despite being lavishly
supported and receiving the best training, however, Waitzkin never made a
GM norm and retired from chess.