The Best Way To Train
Just some personal musings. I know this is debated all the time, and probably the real answer is that there is no right or wrong way to study. On the other hand, I find it interesting to compare my results to my peers who started 'serious' chess around the same time. All of us are rather intelligent, but one only made 1700, another got the NM title but dropped a little below 2200, I made 2300, and another has a GM norm or two - all in approximately the same time frame.
So how did we all do it?
Played in tournaments for about 4 years. He had a couple opening books which he read and knew fairly well. Otherwise he didn't study a whole lot. He tried to learn by playing in tournaments and spending plenty of time in the skittles room. Amusingly, his 'calculation' was often quite deep, but his tactical strength severely limited his accuracy.
Obsessed with openings. I've watched IM's deviate from their own repertoires just to avoid his prep. Unfortunately, he tends to be blunder prone which is likely the result of inadequate tactical practice.
Me. I study a lot of everything. I think I spent too much time as an intermediate player working on openings. I don't play those openings anymore, and I'm inclined to think my time would have been better spent studying games and working on tactics.
Had a GM coach the moment he began to show progress. Read all the 'hard' books (Kasparov's stuff, Aagaards stuff, Dvoretsky's stuff, etc), and spent a ton of time analyzing his losses with his coach. Probably, he will be a GM soon, and so I won't even suggest a flaw in his study method.
What's correct? It looks to me like preparing openings isn't all that important. Everybody needs a repertoire, but preparing brilliant novelties is useless until you're working as a second for Carlsen.
My guess is that tactical training is far and away the most important element of improvement. For those who can't afford a GM coach, picking books that are going to force you to slow down and work at 110% is the way to go. Your training is working when you're frustrated.
Anyways, consider this my two cents. I'd love to hear other's opinions.