Pro hockey players are born, not made, for the most part. I am sure there have been some not-so-talented players become a lot more talented, but for the most part, you are pro-grade material naturally.
Once you reach the level of the NHL, you need to maintain your skills. This is done in a variety of ways, with drills, excersizes, and hockey-specific motions.
Some players like Sidney Crosby, and others are ready to enter the pros right out of high school, basically. Others need to "hone" their skills in a junior league somewhere, or college is all some others need.
There is no really one way, but when it boils down to it, you either have it or you don't.
Some guys spend their whole careers in the minors, and never make it to the pros.....