SI is the highest level of english loved and english major students.Now here is how .
First the most important element is your love and passion on english. You can not learn it well if you do not have passion on that.
Then the ways are so simple but hard to keep on.
Practice your listening. Like Mr zhong's dictation method is very important very useful, you should practice them every day.
Then read more books in english. English is very important to practice by reading more english books.Then you get a sense of english.This is very very important to know about it.
The third method is that do sight interpretation. Try to interpret while you read or hear.
The difficult part is to do two things at the same time you should train that, you can watch two pragrams at the same time, after hearing that you can tell what is the content.
This is my method of self-learning SI.