Here are 6 steps that will help you achieve mastery in any subject or skill. This is the first time I've put these steps in writing, but it is the strategy I have been working on and refining for some time now. This is what I find works best. Mastery of skills or other subjects is a lot of work, but this should help you get there faster.
Mastery Step 1 - Define Your Goal Clearly
The first step to mastery is to get clear on your goals. You've obviously already defined what you want to learn, but try to get even clearer on this. Why do you want to learn it? What benefit will it provide? Do you want to learn enough to get you through a short term goal, or do you want to become an expert?
If you want to become really good at something, it's a good idea to exaggerate this and pretend you are trying to reach the very top; even if you don't think you want to go that far. When I started learning tennis, for example, I imagined I was training for an eventual place in the Wimbledon Final! Since I knew I would never really attempt to get that far, what I was doing was acting. But this gave me the focus I needed to put an incredible amount of effort into each lesson. By reaching for that ultimate goal I would reach my more modest goal much earlier.
Try to place your goals in the real world. Ask: What are you going to use this for? How is it going to benefit your life? While it's easy to become overwhelmed with all there is to learn, most things are actually not worth knowing. Don't waste your time trying to learn something that is worthless.
Mastery Step 2 - Make a plan
When you are sure of what your goals are, it's time to make an initial plan. Take your goal and break it into smaller steps. If you think your plan will take you ten years to complete, what should you have accomplished in 5 years from now; 2 years; 1 year; 6 months; 3 months; 1 month; 1 week; today? These are your sub-goals.
Don't worry if you are unsure how long something will take; this is just to get an idea, so make your best guess. Hopefully it will take much less time than you predicted!
Identify the moments that you will need to encounter to know you have achieved your sub-goals. These should be as objective as possible. You need to be able to accurately measure whether you have achieved them or not. Either you have achieved them or you haven't. If you want to learn a language don't just say you want to be fluent, say you want to be able to read 5 pages of text without needing the dictionary. If you want to play a musical instrument, don't say you want to be good, identify a song and make the performance of that song an indicator that you are good.
Write this down so you have a clear record of where you want to go. This plan will be far from perfect at the moment because you don't know enough about the subject. This is why you will come back and improve the plan a little later down the line.
Mastery Step 3 - Identify existing experts
Your research begins with researching the current experts. Who are the current masters of this subject? If you think you are a pioneer, who most closely resembles a master of this subject? Identify these people by looking for prominent names in books (especially introductions to your subject). When you identify them, memorise their names. Then read everything you can find written by them or about them; study any video you can find of them; and, if possible, get in contact with them. Whether you can meet them or not, these are your mentors.
Choose a mentor who you particularly respect, and commit to following everything they say for a specific chunk of time. Try to find someone whose morals and values resemble your own. If they try to get you to do something you think is wrong, you need to find another mentor. However, if they simply ask you to do something you think is pointless or boring, do it anyway as it is more likely to be important than not.
It's likely that you won't be able to use the best in the field as your private mentor. If this is the case, study them from afar (e.g. in books), and find a good mentor who you can talk with face-to-face. The person you talk face-to-face with should be the one you follow exactly. If the top master disagrees with this person, follow the advice of the one you actually meet rather than what you read in a book. You can always go back to these ideas later, but if you start mixing advice now you will stall your progress.
Mastery Step 4 - Identify Key Components of the Subject
Every subject has elements that are used practically all the time. In a skill these are things like ball-control, grammar, balance... In a knowledge based subject these are such things as jargon terms and the names of the most prominent experts. Spend time identifying these key components. They will be the most important things you learn, so you want to begin learning them as soon as possible.
You've already begun this process in the last step by identifying the experts. Those experts will now help you find the other key components. Look for the words they use the most, the names they often cite, and the things they say are most important. Sometimes they will say things you don't want to hear. They will identify things which you may find boring, hard or even scary. Don't ignore these things because it will only slow your progress.
Mastery Step 5 - Refine Plan
Now you have a better idea of the subject and what is most important, go back and refine your plan. What are the most important things to learn? Learn these first. If you're learning a skill you may come back to these basics throughout your life and specifically try to improve them. For example, if you are learning golf, you would practice your swing for evermore. In other cases these core skills will naturally be honed without thinking about them specifically. For example, when you move up to higher maths, you will still be using basic arithmetic and so naturally get better.
The following two points, give two methods of approaching your learning. You will probably want to incorporate some of each of these methods in your plan.
a) Real life goals
Set some short term goals (under 3 months). These goals should be usable and beneficial to your life, even if you don't learn any more of the subject. Think back to the first step when you defined your goals. Why did you want to learn this subject? Try to incorporate the answer into what you want to learn, while remaining realistic to what you can achieve in a short period of time.
Try to think long term as well. This may be the first step towards a bigger plan and that's a good thing, but make sure it is also useful in the short term. Ideally your goal should also include the key components you identified in step 4. For example, by setting your self the goal of learning a song you will have to master some key techniques on your instrument. These techniques will serve you well as you reach higher mastery of the skill, but learning the song will also be its own reward.
b) Goals with indirect benefits
While it is generally preferential to work towards real life goals, sometimes it's not obvious how what we are learning will eventually be used. But that doesn't make it any less important.
Even more than in step a) you are really relying on the experts here. With the real life goals you could probably identify some key goals without any help. But here the value of the tasks are likely less obvious. Occasionally the experts will make recommendations that are far from efficient and in rare cases, may even be useless, but most the time what they recommend will be truly worthwhile, even if you don't see the worth straight away.
Sometimes the benefit is indirect. For example, by learning to juggle I now seldom drop plates and glasses. This is one of the many side benefits that I wasn't expecting. I couldn't have set the real life goal of not dropping plates, but this indirect goal has helped me there.
Some experts will be able to explain why you should do something; but not all experts will. This isn't because they are less of an expert; they're just lesser teachers. Try to figure out why you are doing something and what ultimate real life benefit it will provide. But if you can't figure out its worth straight away, make sure you carry on doing it anyway. Just because you can't yet see the importance, doesn't mean it isn't important. If possible discuss this with the expert and try to reach an understanding of the task's importance.
Always remember: they are the expert, so they are more likely to be right than you are. Unfortunately they won't always be able to explain why they are right!
When I first started to learn the guitar I was told I should learn scales. While it's quite easy to explain why you should learn scales, some teachers just aren't good at explaining it - or perhaps don't even know. At the time, I put in some effort to learn scales, but not really enough. But when I came back to it, and learnt them in greater detail I began to develop an understanding of why they were important. For example, they helped me improvise and remember parts of some songs, and they were also great training for my fingers. This was true even before I knew the benefits so I could have gone on blind faith, but it certainly helps to understand why you're doing something.
Mastery Step 6 - Review and Repeat
When you have completed your short term goals from step 5 go back to step 1 again. You may be able to get a bit clearer on your ultimate goal now that you have some experience behind you. Also evaluate how you are doing so far. Have you achieved your goals to the level you wanted to? What would you do differently if you were to start again? Perhaps most importantly, have you been able to make real world use of what you have learnt so far? If not, why not?
Use your experience to do even better next time. Go through each of the steps again and refine anything that needs changing. Maybe you have encountered another expert who you now want to follow. Maybe you have identified some more important key components that you now want to learn. And maybe you are clearer about your goals.
Make a new plan based on this information, and then begin training again.
The cycle, of course, is never complete. You will always be able to learn new things. You really can take this as far as you want. On the other hand, the beauty of this strategy is that you achieve short term benefits as well as making progress in the long term. If after 3 months you decide you want to change direction, you will have usable knowledge and/or skills that you can make use of. That time will have truly been invested well.