Input is always the first step in learning. Traditionally, lots of class time is spent on this basic input. For example, one of the traditional techniques is to repeat after teachers many times to get pronunciations right. Now technology can help us quite a bit in this aspect. Students can listen to CDs or audio lessons many times to get the pronunciations and the meanings right.
There is input because we want students to have the right amount of output. From input to output, there is an internalization process. For example, a young boy is learning how to tie a shoelace. His parents need to demonstrate and explain the sequence of tying a shoelace: the first step is ..., then you do this ..., followed by this ... etc. Thus, this boy learns the basic theory of tying a shoelace. However, this does not mean he can do it successfully at the first try, even several tries. He needs to practice on the theory many times. Until one day, he can tie a shoelace very well. We can say he has a successful transition from input to output. At this point, does he need to remember the theory every time when he is tying a shoelace, or he just ties a shoelace without thinking about it? Everybody can look into his/her own experience and say this boy just ties a shoelace without even thinking about it. So what happened to the tying-shoelace theory? An internalization process has happened. The theory of tying a shoelace has been internalized into his practice, his output.
A similar process happens to the students who are learning Mandarin. From input to output, the students need to internalize all the sounds, meanings, grammars and etc. till the point they don't even think about all of these things when they listen and speak. They just do it.
Harder than tying a shoelace, this language internalization requires much more deliberate and targeted practice. It is important for the students to do lots of practice at an appropriate level. The practice shouldn't be too hard, neither too easy. More often than not, people tend to make the practice too hard. For example, a beginner student is encouraged to talk to his/her Chinese friends. Or a student with no knowledge of characters is encouraged to listen to the news. This type of encouragement, often very earnest ones, should not be welcomed.
Once practice is within control, the students can make progress quickly. The basic input is gradually internalized into students' output. After the transition is made, the students do not need to recall all the rules as they carry on a conversation, or express themselves. It's just like we can tie a shoelace without thinking about how to tie it.