What
I found out that not only did the greatest players practice a lot, but they were also very disciplined about what they 
practiced. If you've ever read about John Coltrane's practice regimen you can see that he was not only hard working but thorough. He worked through everything in all twelve keys, working on every variation imaginable; a method well known among jazz players. I also learned that not only does this apply to the greatest players; it was also true of the great composers, songwriters and pretty much anybody else in an artistic discipline. It's not enough to practice; you must be disciplined in figuring out what it is that you have to know and then working through all of the necessary exercises to gain the required knowledge and ability.
There are a lot of ways to find out what it is that you need to learn and it's just a matter of asking the right questions and you'll find the right answers.
Most of the players mentioned had minimal education and some were completely self-taught. The point is that they figured out what it is that they had to learn then spent the necessary time to master those techniques. They were focused about what they had to do. You'll also find that although a lot of these players were self taught and had a style of their own, the method by which they went about learning their craft is very similar. For example, most jazz players go through the same method of learning scales to improvise over complex chord changes. This includes systematically going through all of the different variations of progressions in all keys, in different tempos, with different variations. No small feat that takes a considerable amount of time and focus. The same can be said of composers who learn the necessary theory and then go about working through all of the different ways that the theory can be applied to their craft. Ask Quincy Jones about some of the things he went through when learning his craft.
How
When I teach guitar, I usually treat the lesson like an actual practice session. In other words, I go through all of the things that you should be going through every time you practice. The following is a general list that I start with and then adjust according to the level of the student and their goals. For everybody the basic list is like this:
- WARM UP - 2 minutes
- PICKING EXERCISE - 2
- READING - 5
- EAR TRAINING - 5
- CHORDS - 10
- SCALE - 10
- SONG/REPERTOIRE - 10
Within each general heading there is a few things included that isn't listed in the title. For example chords and scales also include rhythms and theory. I always try to apply the theory to real world examples and songs that they're working on. The picking exercise includes arpeggios and finger-picking. The warm ups are to be done slowly to focus on the left hand and develop independence. This of course is the short list and depending on the student and genre, other headings would be added. For a jazz student, more time would be spent on scales and chords because this would include improvisation and comping. The times are a general indication of how much time to spend on each discipline within a 45 minute practice period. You would spend more time on specific areas when needed; before a big performance for example, the majority of the time would be spent on learning the pieces.
When
I'll be going into more detail about this in the weeks ahead but for now this is a basic outline to give you an idea of how you should approach your time practicing. For every different type of student the list will be slightly different but the idea is the same. Work in the areas that are the most important everyday. Take time out to evaluate what it is that you want to accomplish and then find all the material you can about it. Above is a list for learning a musical instrument; a songwriter's list would be slightly different. By having discipline and working everyday on the things that you know you should (generally your weakest areas) you will learn more and become better in a much shorter time. You will probably surprise yourself.
