There is a rule of thumb that applies to nearly everything you are trying to learn.
For every skill, there is a finite set of fundamentals whose application and combination will allow you to perform that skill.
Thus to succeed at your goal you must:
1. figure out what those fundamentals are
2. figure out what is the correct way to execute those fundamentals
3. Devise and perform a training program to be able to perform said execution from (2) consistently
The usefulness of this advice relies heavily on a clear understanding of the word fundamental in this context. A fundamental is a technique in a finite -but possibly quite large- set of "the fundamentals of skill y." A fundamental is always something that can be trained or improved upon. So, while being tall may be quite important to succeeding at playing basketball, "being tall" is not by our definition a fundamental. In addition, a fundamental cannot be the combination of two or more different fundamentals. The pragmatic reason for this is that if a fundamental is the combination of two other fundamentals, it would be incorrect to train that technique. It would be better to isolate the the two distinct fundamentals that comprise that technique and train them separately. Needless to say, some fundamentals build upon each other in a way that you cannot learn fundamental b without learning fundamental a. Also, while the combination of two fundamentals cannot be a fundamental, the act of combining two fundamentals may very well be a fundamental in and of itself.
With that being clear, we need guidelines on how to perform tasks (1) (2) and (3). Step (1) is often the hardest.
(1)
To figure out the fundamentals of a skill, there are two principal methods that must be combined.
(A) Figuring out the authority on the subject. This is either the best person in the field you can be in contact with, or preferably a book. Then simply inquire from that authority what the fundamentals are.
(B) Reasoning must be used to confirm that a technique is indeed a fundamental of a skill. Of course if you the pioneer of a skill, then this is the only method you can use. This is much harder than simply "downloading" all the fundamentls from an authority, since it can be difficult to figure out the different elements that comprise a technique.
(2)
Once you know what the fundamentals are, then you can begin to judge what is the correct execution of those fundamentals. This is effectively the same process as step one. You consult an authority and combine their advice with rational analysis.
For the sake of example, let us consider the skill of playing tennis. Within that skill is the technique of a serve. We know that a serve, itself, is not a fundamental. This is because a serve is at least the combination of two different fundamentals - an overhead shot and a toss. So let's examine how we would determine the correct way to perform a toss, for our serve, using logic alone.
Of course we want to create the best possible angle for us to hit the ball into our opponents service area, which would mean we want to toss the ball as high as possible. We want to maximize the time the ball stays in the "sweet spot," i.e. the best position for us to hit our overhead shot. This is the highest point at which we can make contact with the ball, so that we can hit the ball at the moment it switches directions (i.e. when its velocity is zero) with the best angle. (etc, etc)
(3)
Once you are aware of what is the correct execution of the fundamentals, you must devise an efficient and regular training plan/schedule to be able to perform all of the fundamentals correctly. From our previous example, this may be something such as:
Toss the ball 10 times trying to hit the height as indicated by a line marked on a wall. Do this with a camera recording your tosses. Review the video and fix mistakes. Repeat 3x 4 days a week.
It is important to remember that when training, mindlessly repeating an action does not help you towards your goal. Only when you are self analytic, by doing an action like recording yourself with a camera and fixing your mistakes, do you make progress. Once again, consulting an authority figure on how to train is often wise. A secret code in the title of books that help you with this stage of learning is "training manual."