Mr. Suzuki said you need several things to do well in music lessons, indeed in most skills. He said:
1) Start as young as possible. It's not impossible to learn a new skill when you're older, but your intuitive learning speed is fastest when you are young. The right age is when your child can stand in one place for half an hour and take instructions from an adult for that amount of time. This age differs for different children and families. It can be as young as 3 or as old as 8 or 9. Younger is better. Parents know when this would be possible for their child.
2) Music is learned like talking. You learned how to talk because you were surrounded by people talking. He pointed out that very few people don't learn how to talk. He said if you want to be musical, surround yourself with the sound of music. You will absorb it, like you did language. We all know of people who went to another country and almost immediately started absorbing and speaking that language when they were surround by it. Suzuki said that the same thing happens with music. He said that a long time ago, musical people come used to come from musical families because they were the only people who got to hear music a lot. Now everyone has access to music and can surround themselves with the sound of music. Because of this, nowadays many musicians come from families where nobody before them ever played an instrument!
Mr. Suzuki was insistent on the inherent value of classical music, so the Suzuki Method is classically based. He strongly believed that it had qualities that created better people if listened to enough. Nevertheless, many Suzuki-trained musicians are fluent in many other types of music, and their classical training gives them enough technique to play just about any type of music they have heard enough when they are older.
3) A parent needs to guide home practice of a young child for a number of years, until the student's skill set is developed, and he or she practices efficiently and no longer wants the parent's help (and students often tell you when that is, though parent and teacher enter into this discussion and often know best). Suzuki teachers teach both the student and the parent at the lesson. The parent doesn't need to play, but needs to have enough knowledge about what the young student is trying to learn to be able to assist home practice daily. This is very different from what many people think when they think of music lessons. Suzuki said the beginning is important and difficult to get right, that it takes the oversight of someone older and wiser than a five-year-old. If the family situation makes this impossible, you can start at 10 when it can be entrusted to the student, but younger is better. Also, a special bond develops between the parent and student in Suzuki lessons; there is often nothing else in daily life that they do together every day, and they get to know each other very well through this daily interaction. It is old-fashioned, I-learned-it-from-my-parent style learning. This is especially important today, when people often interact more with their phones and tablets than the other people in the room with them, and thus become disconnected from each other.
4) Most skills are learned over a number of years, and music is no exception. Suzuki correctly pointed out that many people try a number of skills briefly, giving up on each one in turn and ending up doing none of them well. He felt music was one of the most valuable of skills, that developed skill in music affects almost every area of one's life positively. He said one should expect to learn it like math or reading, little by little over a number of years. Why do people treat acquisition of skill in music differently from acquiring skill in math or reading? Does a "hockey family" give up on the child who doesn't skate very fast or great stick-handling skills within two or three years? Do they throw in the towel and say, well, maybe it's not for you? Not in my experience, but people do this for music. Do people say, well, math is tough for you so you should try something else? Not if they see it as a life skill. Well, that's what Suzuki was saying about music: that it's a life skill, that's the way it is to be viewed he said. And this is very different from how many people see music lessons, and one of the main reasons they fail, because people very often give up before they have a chance to succeed.
5) Suzuki said "Practice on the days you eat." So much of what he said is simple maxims that we intuitively know. If you want to get skillful at doing something, do it every day. The amount of time varies per person, but more is better. Half an hour is a bare minimum, think more like 5 minutes per year of age until it becomes unreasonable!